How to measure internal blinds for an inside mount

Measure the recess width at the top, middle and bottom, and the recess height (drop) at the left, center and right. Record all six measurements, then use the width and drop specified by your chosen blind’s ordering guide. Do not assume every blind uses the shortest height. Measure the recess depth and confirm it meets your product’s minimum, allowing for obstructions like window handles. Use a metal tape measure. For a supplier that asks for recess dimensions and makes its own fit deductions, provide those dimensions without subtracting an extra allowance. Other products may require finished sizes or a different method; check before ordering (Blinds To Go: How to Measure Inside Mount; Blinds 2go: Recess Fitting).

What to check before you start

- Use a metal tape (cloth tapes can stretch). Clear the sill and note any tiles, beading, or handles that narrow the opening. Check you have enough depth to fit the headrail and brackets, including clearance for handles. Blinds 2go publishes minimum recess depths by blind type and advises measuring in three places, using the smallest numbers. They also note tiles part-way up a recess are often the narrowest point and should be measured between the tiles (Blinds 2go: Recess Fitting).

Step-by-step: inside-mount measuring

1) Measure width in three places

Measure the internal width at the top, then the middle, then the bottom of the recess. Pull the tape straight and record each value with units. Use the smallest width for your order so the blind won’t bind if the frame isn’t perfectly square (Blinds To Go: Inside Mount; Blinds 2go: Recess Fitting).

Roller-blind note: some suppliers ask you to measure roller-blind width at the top of the recess so the blind fits tightly at the head. Blinds 2go specifies this and will do deductions for you (Blinds 2go: Recess Fitting).

2) Measure drop (height) in three places

Measure the internal drop at the left, center, and right. Use the drop required by that specific product’s instructions. Blinds 2go’s general recess guide says to use the smallest measurements; do not generalise that choice to a product with different instructions (Blinds To Go: Inside Mount; Blinds 2go: Recess Fitting).

3) Measure depth and check obstructions

Measure the usable recess depth (the space available to install the blind) and confirm it meets your product’s minimum. Account for handles or beading that project into the recess. Blinds 2go lists typical minimum depths for popular blind types and advises checking handle clearance (Blinds 2go: Recess Fitting).

Worked example for a product using the smallest-width and smallest-drop method

- Widths: Top 825 mm, Middle 822 mm, Bottom 823 mm → Order width = 822 mm (smallest).
- Drops: Left 1452 mm, Center 1450 mm, Right 1451 mm → Order drop = 1450 mm (smallest).
- Depth: 55 mm clear to the nearest obstruction. If your chosen blind’s minimum recess depth is 50 mm, that example meets the stated depth requirement; you must still check bracket, headrail and handle clearances. If it needs 70 mm, choose a different product or consider an outside mount (Blinds 2go: Recess Fitting).

Tiles, narrow spots and not-quite-square frames

If part of the recess is tiled (common in kitchens and bathrooms), measure between the tiles where the opening is usually narrowest and use that value. For an out-of-square frame, retain all measurements and ask the supplier about the usable opening and fit limits; taking one smallest number is not a universal correction for a crooked recess (Blinds 2go: Recess Fitting).

Recording and communicating your measurements

How to write it down

Label clearly: “Inside mount.” Note units on every line. Example: Width 822 mm (top 825, middle 822, bottom 823); Drop 1450 mm (L 1452, C 1450, R 1451). Blinds To Go describes taking width and height at three positions. Blinds 2go’s general recess guide specifies the smallest measurements and its own manufacturing deductions. Use the instructions for the supplier and product you actually order (Blinds To Go: Inside Mount; Blinds 2go: Recess Fitting).

Depth requirements vary by product

Minimum recess depth depends on blind type and headrail. Verify your product’s spec before ordering. Blinds 2go provides a depth table and notes to consider handle clearance (Blinds 2go: Recess Fitting).

When to pick inside mount (and when not to)

Choose inside mount for a clean, built-in look and when recess depth meets the product’s minimum. If depth is insufficient or you need to cover trim or gaps, use an outside mount and add overlap to reduce light gaps (Blinds 2go: Exact Fitting).

Common mistakes to avoid

• Measuring in one spot only. Always do top/middle/bottom for width, and left/center/right for drop (Blinds To Go; Blinds 2go).
• Forgetting depth or handle clearance. Confirm usable depth against product requirements (Blinds 2go).
• Making your own deductions. Most suppliers do this for you when you specify inside mount (Blinds 2go).

Inside-mount measuring checklist

• Measure recess width at top, middle, bottom; write down the smallest with units
• Measure drop at left, center and right; record all three and follow the product’s height-ordering rule
• Measure usable recess depth and confirm your product’s minimum (allow for handles)
• Note any tiles or beading and measure between them if they narrow the opening
• State “inside mount” on the order; let the supplier apply any factory deductions

Helpful related reading from Home by Doing

• How to use a spirit level vertically (to check plumb) for frames you suspect aren’t square.
• Can you screw directly into plaster walls? if you later plan an outside mount over plaster.

FAQ

Do I give recess size or finished blind size?

Give the measurement type the selected product asks for: recess size or finished size. If the supplier makes its own deduction, do not deduct again. Retain every measurement and check the ordering rule for width and drop (Blinds 2go: Recess Fitting).

What if my roller blind needs to fit tightly at the top?

Follow your supplier’s product note. Blinds 2go advises measuring roller-blind width at the top of the recess and they apply any required deductions (Blinds 2go: Recess Fitting).