How to Measure Blinds: A Step-by-Step Guide

There’s an old saying in the trade: “Measure twice, order once.” In the world of blinds, nothing could be more vital. It’s not just about saving money, it’s about getting it right the first time. Imagine ordering a tailored suit and receiving one that doesn't fit; it's frustrating, and it costs you. The same misalignment applies when blinds arrive too small, too long, or simply out of step with your home’s décor.

In this guide, you’ll learn exactly how to measure your windows for blinds, whether you’re opting for a ready-made solution or investing in made-to-measure craftsmanship. We’ll cover everything from tools to techniques, inside and outside recess measurements, and common mistakes that trip up even the most confident DIYers.

If you’re considering a customised option, there are several benefits of made-to-measure blinds that can elevate both function and style in your home.

And if you're shopping from Lister Cartwright, this guide ensures you’ll be ready with the right measurements before you even browse.

What You’ll Need Before You Start

To achieve precise results, select only professional-grade tools:

• Steel measuring tape (in millimetres; fabric tapes can stretch)
  

• Pencil & notepad (or our downloadable measuring checklist)
  

• Step stool or ladder
  

• Spirit level (for bracket alignment)
  

• Calm focus (and double-checking measures)

Preparation sets the stage for perfection.

Made-to-Measure Measurements: Recess Size vs Exact Size

You’ll often encounter two key phrases: recess size and exact size. They’re not interchangeable. Here's the difference:

Which Should You Choose?

If you’re installing inside the recess, go with recess size and let the manufacturer make the deductions (typically 10mm to 15mm on width). If you're mounting outside the recess, or you know your exact design needs, select the exact size. Now, let’s talk about how to get these measurements right. 

How to Measure for Inside Recess Blinds

Measurement Steps:

• Measure the width at the top, middle, and bottom -  record the smallest.

• Measure the drop at left, centre, right -  record the smallest.

• Check recess depth (minimum 60 mm for most blinds).

• Use millimetres, not centimetres.

Inside Recess Table (Example Value)

This is an example table filled with sample values to demonstrate proper use (you can adjust these with your actual measurements):

Key Notes:

• Venetian, roller, Roman, and cellular blinds need clearance for headrails.

• Vertical blinds need additional height for louvre stacking.

• Tip: Don’t deduct allowances; let the blind-maker handle that precisely.

How to Measure for Outside Recess Blinds

Measurement Steps:

• Measure desired width and drop, adding:

• 50 - 100 mm per side for width

• 100 - 150 mm above the window for drop (brackets and style)

• Use millimetres for consistency.

Outside Recess Table (Example Value)

This is an example table filled with sample values to demonstrate proper use (you can adjust these with your actual measurements):

Tip: This coverage strategy blocks light gaps and makes windows appear larger.

How to Measure for Made-to-Measure Blinds (Step-by-Step)

1. Use a metal measuring tape. Flexibility equals risk, so avoid cloth tapes at all costs.
   

2. Measure the width and drop three times each.
   

• Recess fit: Take width measurements at the top, middle, and bottom of the recess. Record the smallest.
  

• Drop (height): Measure at the left, centre, and right. Record the shortest.
  

• Exact fit: Measure the desired width and height of your finished blind, including any overhang.
  

3. Make notes of any obstructions, such as window handles, locks, or uneven plastering.
   

4. Check depth clearance is particularly important for Venetian, vertical, or roller blinds where the headrail requires space to mount and operate.
   

PS: Double-check your supplier’s guide. At Lister Cartwright, for instance, our measuring recommendations are tailored to each blind type to eliminate guesswork. Find ours here. 

Common Measuring Mistakes to Avoid

In a world where millimetres matter, it’s easier than you think to go wrong. Here’s a list of missteps we’ve seen time and time again, and how to steer clear.

• Using a fabric measuring tape:  it sags, warps, and lies.

• Measuring just once: it only takes a warped sill or an uneven recess to throw off accuracy.

• Assuming all windows are the same size:  even in new builds, window dimensions can vary.

• Mixing width and drop:  always label your figures clearly.

• Rounding up numbers: never “clean up” your figures; provide the raw data.

• Overlooking inside vs outside fit:  each requires a different strategy and deduction.

• Ignoring window depth: some blinds need up to 75mm clearance for brackets and mechanisms.

• Failing to level:  crooked brackets equal a crooked blind.

• Neglecting obstacles, such as window handles, vents, tiles, or curtain rods, can interfere with operation.

• Measuring with one eye on the clock:  precision takes time. Don’t rush it.
  

Also Read: Common Curtain & Blind Issues and How to Fix Them

Looking forward? Maintaining your blinds after installation is essential in preserving their beauty and function. Our guide provides an effortless approach to cleaning all types of blinds. Check out our guide on How to Clean Your Blinds: Easy Method.

Quick Self‑Check List Before Ordering

Before sending off your order, review this checklist. It’s the difference between satisfaction and frustration.

• Measured three times at multiple points (top/middle/bottom or left/middle/right)

• Recorded the smallest value for recess measurements

• Used a metal measuring tape

• Maintained consistent UK metric units

• Clearly labelled width and drop separately

• Chosen inside or outside fit, not both

• Checked for obstructions like handles or tiling

• Confirmed sufficient window recess depth for headrail or brackets

• Ensured brackets are level

• Double-checked all figures before submission

• Know your blind type for the home
  (e.g., roller, Roman, vertical) and operation style (manual or chain). For more details, read more on The Ultimate Guide to Roman Blinds: Styles, Materials, and Benefits.

• Identified whether you’ll need brackets, liners, or chain lengths

• For extra peace of mind: Use Lister Cartwright’s measuring Guide (available on our site)

Before you spend a penny, print your measurements and double-check. This guide ensures accuracy, lowers returns, and raises satisfaction, just the way a signature window treatment should. 

If you’ve followed this guide, measured three times, used a metal tape, and accounted for every obstruction and allowance, then you're not guessing. You're ready. But don’t stop at the blind alone. A made-to-measure blind is only as good as the parts that support it. That’s why at Lister Cartwright, we offer everything you need to finish the job right:

• Curtain poles and clean-lined brackets that hold firm

• Linings that block heat or light when required

• Chain lengths for easy operation that cut to your preference

• Finishing hardware designed to fit your window, not the other way around
  

It doesn’t cost more to do it right. It only takes a little more thought. Before placing your order, ask yourself: Have I measured carefully? Do I have everything I need to fit, fix, and finish? Do I want a blind that simply fits or one that fits perfectly? If the answer is the latter, choose Lister Cartwright’s made-to-measure blinds. Built to measure. Built to last and built for your home.