Getting your vertical blinds measurements right is the difference between a flawless fit and a frustrating installation. Before ordering made-to-measure blinds, you'll need to determine whether you're fitting inside the window recess or outside it, accurately measure the blind width and blind drop, and account for any obstructions, recess depth limitations, or window sill projections.

For recess fit blinds, always measure the width and height in three places and use the smallest measurement. For outside recess fitting, measure beyond the window opening to allow sufficient overlap for light control and privacy. Using a metal tape measure, recording exact dimensions, and checking for blind brackets clearance can help avoid costly measuring errors.

Whether you're measuring a living room window, patio doors, or a large office opening, this guide covers everything you need to know before ordering custom vertical blinds.

How to Measure Windows for Vertical Blinds Without Making Costly Mistakes

Vertical blinds remain one of the most versatile window coverings available. Their ability to control light, maintain privacy, and suit everything from compact windows to expansive patio doors makes them a favourite choice for modern homes.

However, even the highest-quality blinds can disappoint if the measurements are inaccurate.

Many homeowners focus on fabric colours and styles first, only to discover later that the blind dimensions were recorded incorrectly. A blind that is too narrow leaves unwanted gaps. A blind that is too long may drag across the window sill or flooring. Neither outcome is ideal.

Before browsing the full collection of Vertical Blinds, it is worth spending a few minutes understanding the correct measuring process.

Accurate measurements taken today can save hours of adjustment, returns, and installation headaches later.

Why Accurate Measurements Matter

When ordering made-to-measure blinds, manufacturers build the blind according to the exact figures provided. Unlike ready-made alternatives, there is very little room for error.

Accurate measurements help ensure:

Smooth blind installation
Proper operation of the blind track
Consistent coverage across the entire window opening
Improved privacy
Better light control
A cleaner, more professional appearance
Correct positioning of the headrail and vertical slats

Even a difference of a few millimetres can impact the finished result.

This becomes especially important for large windows, bifold doors, and patio door installations where precise alignment is highly visible.

Understanding the Two Main Fitting Types

Before taking a single measurement, you must decide how the blind will be mounted.

There are two primary fitting methods:

Inside recess fitting
Outside recess fitting

The measuring method differs significantly depending on which option you choose.

Inside Recess Fitting

An inside recess fitting positions the blind neatly within the window recess.

This creates a streamlined appearance and allows the blind to sit within the architectural lines of the window frame.

An internal recess installation works particularly well when:

The recess depth is sufficient
The window opening is square
There are no major obstructions
A minimalist appearance is preferred

When measuring a recess fit blind, manufacturers will typically make the necessary blind deductions during production.

Because walls are rarely perfectly straight, measurements should always be taken at multiple points.

Outside Recess Fitting

Outside recess fitting, sometimes referred to as a face fit blind installation, positions the blind outside the window opening.

This approach is often chosen when:

The recess depth is too shallow
Handles protrude into the recess
The window opening is uneven
Maximum light blockage is desired
The homeowner wants the window to appear larger

Many homeowners selecting premium collections such as the Day & Night Vertical Sheers prefer an outside recess fitting because it showcases the fabric more prominently while creating a luxurious finish.

Tools You'll Need Before Measuring

Professional installers keep their measuring process simple.

Gather the following tools before you begin:

Metal tape measure
Pencil
Notepad
Step ladder if required
Spirit level (optional)
Measuring checklist

Avoid using:

Cloth tape measures
Flexible sewing tapes
Phone measuring apps
Estimations

A rigid metal tape measure provides the most reliable window frame measurement and helps maintain accuracy over larger spans.

How to Measure for Vertical Blinds Inside a Recess

Measuring vertical blinds inside a recess requires precision.

Never assume that the top, middle, and bottom of the recess are identical.

In many homes, subtle variations exist due to plasterwork, settlement, or previous renovations.

Step 1: Measure the Width

Take three separate width measurements:

Top width
Middle width
Bottom width

Record each measurement carefully.

For example:

Position	Width
Top	1200mm
Middle	1197mm
Bottom	1195mm

In this example, the smallest measurement is 1195mm.

This is the figure that should be supplied when ordering recess fit blinds.

Using the smallest measurement helps prevent the blind from catching against the sides of the window recess.

Step 2: Measure the Drop

Next, measure the height of the recess.

Take measurements from:

Left side
Centre
Right side

Again, record all figures and use the smallest measurement.

This ensures the blind drop fits comfortably within the available space without rubbing against the window sill.

Step 3: Check for Obstructions

Before finalising your measurements, inspect the recess carefully.

Common obstructions include:

Window handles
Security sensors
Ventilation units
Decorative mouldings
Radiator pipes

These features may affect blind mounting position and could require an alternative fitting method.

For example, homeowners choosing patterned options such as the Herringbone Designer Cream Yellow Vertical Blinds often prefer to maximise fabric visibility, making an outside recess installation a practical solution when recess obstacles are present.

Measuring Recess Depth Correctly

One of the most overlooked aspects of measuring windows for blinds is recess depth.

A recess may appear suitable at first glance but lack the clearance space required for the blind headrail and vertical slats.

To check recess depth:

Measure from the front edge of the recess to the glass.
Measure in several locations.
Identify the shallowest point.
Check for protruding handles or locks.

Insufficient recess depth can prevent the blind from operating correctly and may lead to fabric contact with handles or other hardware.

A quick depth check now can prevent installation issues later.

In the next section, we'll cover outside recess measurements, overlap calculations, measuring patio doors and large windows, common vertical blind measurement mistakes, and professional tips used by installers to achieve perfect results every time.

How to Measure for Vertical Blinds Outside a Recess

When a window recess is too shallow, uneven, or obstructed, fitting the blind outside the recess often delivers better results.

An outside recess fitting allows the blind to extend beyond the window opening, helping improve privacy, reduce light leakage, and create a more balanced appearance. It can also make smaller windows appear larger and more prominent within a room.

Unlike recess fit blinds, where the smallest measurement is used, an outside recess fitting requires you to calculate the finished blind size yourself.

Step 1: Measure the Window Opening Width

Begin by measuring the full width of the window opening.

Take measurements across the widest points of the opening and record the largest figure.

Step 2: Add Overlap

To maximise coverage, additional width should be added beyond the window frame.

A common recommendation is:

75mm to 100mm overlap on each side
Greater overlap where space allows

For example:

Window Width	Side Overlap	Finished Blind Width
1200mm	100mm each side	1400mm

This additional blind overlap helps minimise light gaps and improves privacy, especially during evenings when interior lights are switched on.

Step 3: Measure the Blind Drop

Measure from the intended fixing position down to the desired endpoint.

Possible finishing points include:

Just below the window sill
To the floor
Over patio doors
Full-height glazing

Always double-check the measuring drop to ensure furniture, radiators, and flooring transitions do not interfere with operation.

How Much Overlap Should Vertical Blinds Have?

One of the most common questions homeowners ask is how much overlap is necessary.

While every installation differs slightly, the following guidelines generally work well:

Side Overlap

Minimum: 50mm per side
Recommended: 75mm–100mm per side

Top Overlap

Recommended: 75mm–150mm above the window opening

Bottom Overlap

Window installations: 25mm–50mm below sill
Full-length installations: Stop just above floor level

Adequate overlap not only improves aesthetics but also enhances light control and thermal efficiency.

A well-planned outside recess fitting can dramatically improve the appearance of even the simplest blind design.

Measuring Patio Doors for Vertical Blinds

Vertical blinds have long been a popular solution for patio doors thanks to their practicality and smooth operation.

However, patio door measurements require additional consideration.

Check Door Clearance

Before taking measurements, determine:

Which direction the door opens
Handle projection distance
Available fixing space above the frame
Any nearby walls or obstructions

The blind track must operate freely without interfering with door movement.

Measure the Full Opening

Measure:

Total width of the glazed area
Total height from fixing point to floor

Do not simply measure the glass itself.

The blind should comfortably cover the complete opening while maintaining sufficient side overlap.

This is particularly important when selecting statement fabrics such as the Pencil Stripe Autumn Sunset Vertical Blinds, where consistent fabric coverage contributes significantly to the finished look.

Measuring Large Windows for Blinds

Large windows can transform a room with natural light, but they also amplify measuring mistakes.

The larger the opening, the more important precise measurements become.

When measuring large windows:

Use a metal tape measure rather than laser estimates
Measure multiple times
Record measurements in millimetres
Verify squareness of the opening
Check mounting surfaces thoroughly

Large spans may require stronger fixing points and additional blind brackets to support the weight of the headrail.

Where uncertainty exists, taking a second set of measurements on another day can help eliminate errors.

Measuring Bay Windows for Vertical Blinds

Bay windows often present unique challenges due to their angled construction.

Each section should be measured independently.

Important Considerations

Measure every window individually
Record each width measurement separately
Account for corner clearances
Consider blind stack width when opened
Check for protruding handles

Because bay windows vary dramatically in design, there is rarely a one-size-fits-all measurement approach.

Careful planning before ordering custom vertical blinds can prevent alignment issues during installation.

Common Vertical Blind Measurement Mistakes

Even experienced DIY enthusiasts occasionally make errors when measuring windows.

Fortunately, most mistakes are entirely avoidable.

1. Measuring Only Once

Always measure at least twice.

Professional installers frequently verify dimensions multiple times before ordering.

2. Using the Largest Recess Measurement

For recess fit blinds, the smallest measurement matters.

Using the largest figure may result in blinds that physically cannot fit within the opening.

3. Forgetting About Window Handles

Handles are one of the most common causes of fitting problems.

Even a perfectly measured blind width and blind drop can become problematic if handles protrude significantly into the recess.

4. Ignoring Recess Depth

Many homeowners focus exclusively on width and height.

Without sufficient recess depth, the blind headrail may not fit properly or operate smoothly.

5. Measuring in Centimetres

Millimetres provide far greater accuracy.

Always record exact measurements in millimetres when ordering made-to-measure blinds.

6. Estimating Overlap

Outside recess fitting requires deliberate planning.

Guessing side overlap often results in insufficient coverage and visible light gaps.

A Simple Blind Measuring Checklist

Before placing an order, confirm the following:

Window width measured three times
Window height measured three times
Smallest measurement identified
Recess depth checked
Obstructions identified
Blind mounting position confirmed
Overlap calculated
Measurements recorded in millimetres
Installation surface inspected
Measurements verified a second time

Completing this checklist dramatically reduces the risk of ordering errors.

Choosing the Right Blind Style After Measuring

Once measurements have been confirmed, selecting the right fabric and finish becomes much easier.

Bright, contemporary spaces often benefit from lighter shades that enhance natural light, while darker fabrics can introduce contrast and sophistication.

For minimalist interiors, the Pencil Stripe Brilliant White Vertical Blinds provide a clean, timeless appearance that works particularly well across larger window openings.

For more dramatic spaces, deeper tones can create visual depth while maintaining all the practical advantages that make vertical blinds such a versatile window covering solution.

In the final part of this guide, we'll cover professional blind measuring tips, exact size versus recess fit blinds, child safety considerations, blind installation preparation, and how to confidently order your made-to-measure vertical blinds online.

Exact Size vs Recess Fit Blinds: Understanding the Difference

One of the final decisions you'll encounter when ordering made-to-measure blinds is determining whether to provide exact finished sizes or recess measurements.

Although the terms are sometimes used interchangeably, they refer to two very different approaches.

Recess Measurements

When ordering using recess measurements:

You provide the exact size of the window recess.
The manufacturer applies appropriate blind deductions.
The finished blind is slightly smaller than the opening.
The blind operates freely within the recess.

This is typically the simplest option for homeowners because the necessary manufacturing adjustments are handled for you.

Exact Size Blinds

When ordering exact size blinds:

You provide the finished blind dimensions.
No deductions are applied.
The blind is manufactured to the precise measurements supplied.

This option is most commonly used for outside recess fitting where the customer has already calculated the required overlap and final blind size.

Before placing an order, always confirm which measurement method is being requested.

Professional Blind Measuring Tips

Professional installers often follow a few simple habits that dramatically improve measuring accuracy.

These small details can make a substantial difference to the finished result.

Measure at Different Times of Day

Natural light changes how window openings appear.

A second measurement taken later in the day can help reveal details that may have been overlooked initially.

Record Every Measurement Immediately

Avoid relying on memory.

Write measurements down as soon as they are taken.

Many measuring mistakes occur not because the dimensions were wrong, but because the correct figures were not recorded accurately.

Use Millimetres Only

Mixing units can create confusion.

For consistency:

Measure in millimetres
Record in millimetres
Order in millimetres

This eliminates unnecessary conversions and improves precision.

Check Fixing Surfaces

Before ordering, inspect the intended mounting surface carefully.

Ensure there is sufficient room for:

Blind brackets
Headrail installation
Smooth operation of vertical slats
Child safety devices

Strong fixing points contribute significantly to long-term blind performance.

Blind Installation Preparation

Accurate measurements are only one part of a successful project.

Preparing the installation area beforehand can help ensure a smoother fitting process.

Clear the Area Around the Window

Remove:

Furniture
Decorative items
Plants
Fragile accessories

This provides unrestricted access during installation.

Inspect the Wall Condition

Look for:

Crumbling plaster
Uneven surfaces
Hidden pipework
Electrical cables

A secure fixing surface helps maintain proper alignment and operation.

Confirm Headrail Position

Before drilling, verify:

Headrail clearance
Window handle clearance
Blind stack position
Opening direction

These checks help prevent adjustments later.

Child Safety Considerations

Modern blinds should always be installed with safety in mind.

Where chain-operated mechanisms are present, ensure child safety devices are fitted according to current regulations and manufacturer recommendations.

Important considerations include:

Securing operating chains
Maintaining recommended clearance heights
Following installation instructions carefully
Keeping cords away from furniture that could be climbed

Safety should be considered during both measurement and installation stages.

How Blind Stack Width Can Affect Your Measurements

Many buyers focus exclusively on blind width and blind drop while overlooking blind stack width.

When vertical blinds are fully opened, the slats gather together into a stack.

The size of this stack depends on:

Blind width
Number of slats
Fabric thickness
Headrail system

For patio doors and large glazed openings, understanding stack width can help maximise your available view when the blinds are open.

If unobstructed access is important, consider where the stack will sit once the blind is fully drawn back.

Measuring Awkward Windows for Vertical Blinds

Not every window is perfectly square.

Older properties, extensions, and renovated homes often present unusual measurement challenges.

When measuring awkward windows:

Take additional measurements.
Check for uneven walls.
Measure diagonally to assess squareness.
Identify protrusions and obstructions.
Confirm recess depth throughout the opening.

A little extra preparation can prevent surprises during blind installation.

Where significant irregularities exist, outside recess fitting often provides the most forgiving solution.

Selecting the Right Fabric After Measuring

Once the measurements have been confirmed, attention can shift towards choosing the ideal fabric.

The style you choose should complement both the room and the practical requirements of the space.

For bright, modern interiors, the subtle texture of the Pencil Stripe Agate Gray Vertical Blinds offers a contemporary finish that pairs well with neutral décor schemes.

For rooms where a stronger visual statement is desired, the bold contrast of the Pencil Stripe Black Licorice Vertical Blinds can create a sophisticated focal point while maintaining excellent functionality.

The right fabric choice enhances the precision of your measurements by ensuring the finished installation looks intentional, balanced, and professionally fitted.

Final Thoughts

Measuring windows for vertical blinds is not difficult, but it does require attention to detail.

By understanding the difference between inside recess fitting and outside recess fitting, measuring width and drop correctly, checking recess depth, accounting for overlap, and identifying potential obstructions, you can achieve highly accurate measurements with confidence.

Remember these key principles:

Use a metal tape measure.
Measure in millimetres.
Measure width and height three times.
Use the smallest measurement for recess fitting.
Check recess depth carefully.
Allow adequate overlap for outside fitting.
Verify measurements before ordering.

Taking the time to measure properly helps ensure your made-to-measure blinds fit beautifully, operate smoothly, and provide years of reliable performance.

Whether you're covering a compact bedroom window, a large bay installation, or expansive patio doors, careful planning and accurate measurements are the foundation of a successful result.

Explore the full range of premium vertical blind options available from Zen Blinds and order with confidence knowing your measurements are accurate from the very beginning.

Frequently Asked Questions

Can I measure for vertical blinds by myself or should I hire a professional?

Most homeowners can successfully measure for vertical blinds themselves using a metal tape measure and a careful approach. As long as you take multiple measurements, record them accurately, and follow a reliable measuring guide, professional assistance is usually unnecessary for standard windows and doors.

Should I measure before or after replacing my windows?

Always measure after new windows have been fully installed. Even small differences in frame dimensions, plasterwork, or window positioning can affect the final blind size. Measuring before installation may result in blinds that no longer fit correctly.

How precise do my measurements need to be?

Vertical blinds should be measured to the nearest millimetre. Avoid rounding measurements up or down, as even small inaccuracies can affect how the blind fits and operates. Precise measurements are especially important for recess fit blinds.

Can vertical blinds be fitted to uPVC windows?

Yes. Vertical blinds can be installed on or around uPVC windows. However, many homeowners prefer fixing blinds to the wall or ceiling rather than directly into the window frame. Always check manufacturer recommendations before drilling into uPVC.

What happens if my window recess is not perfectly square?

This is very common, particularly in older properties. Measure the width and height in multiple places and follow the recommended measuring method. For severely uneven openings, an outside recess fitting can often provide a cleaner and more forgiving finish.

How much space is needed above a window for vertical blinds?

The amount of space required depends on the headrail system and mounting method. Most installations require sufficient room for the blind brackets and operating mechanism. If space above the window is limited, a face-fit installation may be a better option.

Can I install vertical blinds on ceiling mounts?

Yes. Vertical blinds can be fitted to ceilings as well as walls. Ceiling mounting is particularly popular for patio doors, full-height windows, room dividers, and modern open-plan spaces where a sleek appearance is desired.

Do I need different measurements for blackout vertical blinds?

The measuring process remains the same. However, if maximum light control is important, many homeowners choose additional overlap on outside recess installations to reduce light leakage around the edges of the blind.

How do I measure corner windows for vertical blinds?

Corner windows should generally be measured as separate sections unless a specialist blind system is being installed. Accurate measurements for each window section help ensure smooth operation and proper alignment once fitted.

Is there a minimum or maximum size for vertical blinds?

This varies depending on the manufacturer and blind system. Most made-to-measure vertical blinds can accommodate both small residential windows and large patio door openings. Always check the specific product specifications before ordering unusually large or unusually narrow blinds.

How to Measure Windows for Vertical Blinds the Right Way