Measuring your windows for blinds is the one step you cannot afford to rush. Get it right, and your blinds fit cleanly, operate smoothly, and look intentional. Get it wrong, and even premium blinds will disappoint.
This guide explains how to measure windows for blinds accurately, whether you are fitting inside the recess or mounting outside the window frame. You will learn what tools you need, how to measure different blind types, and how to avoid common mistakes that lead to poor fit. Follow this process once, carefully, and you set yourself up for blinds that work as they should, first time.
If you prefer visual support while reading, you can cross-reference this article with Blindsonline’s detailed measuring guide at any point.
What You’ll Need Before Measuring Your Windows
Before you start measuring, prepare the basics. Accuracy depends on consistency and method, not speed.
- Steel tape measure (fabric tapes stretch and distort results)
- Pen and paper or a notes app
- Stable step stool for taller windows
- Clear lighting
Measure in millimetres only. Switching units midway introduces errors that are difficult to correct later.
Inside Mount (Recess) vs Outside Mount (Face): Know the Difference
Before taking measurements, decide how the blind will sit. This single choice determines every number that follows.
Measuring Windows for Inside Mount (Recess) Blinds
Inside mount blinds sit neatly within the window recess. They offer a clean, architectural finish and suit modern interiors.
How to measure an inside mount:
- Measure the width at the top, middle, and bottom of the recess
- Record the smallest width
- Measure the drop on both the left and right sides
- Record the longest drop
Always check recess depth. Some blind styles require minimum depth to sit flush. If the recess is shallow, the blind may project forward.
CTA (contextual): If you want a visual breakdown of recess depth and bracket clearance, consult the full Blindsonline measuring guide before ordering: https://blindsonline.co.za/measuring-guide/.
Measuring Windows for Outside Mount (Face) Blinds
Outside mount blinds are fixed over the window opening, either on the wall or the frame. They offer better coverage and are more forgiving in older homes.
This option works best when:
- Recesses are shallow or uneven
- Maximum light block-out is required
- Window frames are not square
How to measure an outside mount:
- Measure the width of the area you want the blind to cover
- Add extra width on each side (usually 50–100mm per side)
- Measure the full drop from the mounting point to the desired finish point
Outside mounts are often the safest choice when accuracy or depth is uncertain.
How to Measure Different Blind Types
Blind styles differ in how they operate and stack. Measuring must account for these mechanics.
Roller Blind Measurements
Roller blinds rely on clean alignment.
- Measure width and drop based on mount type
- Allow space for brackets and chain controls
- Check that window handles will not interfere
Roller blinds reward precise measurements. Small inaccuracies remain visible once installed.
Venetian Blind Measurements
Venetian blinds require clearance for slat movement and controls.
- Measure recess width carefully
- Confirm enough space for tilt and lift mechanisms
- Avoid tight widths that restrict slat rotation
Roman Blind Measurements
Roman blinds stack fabric at the top when raised.
- Allow for fabric stacking height
- Measure drop accurately to prevent bunching
- Outside mount is often preferable for a balanced look
If you are still deciding on blind styles, explore Blindsonline’s blinds articles to match design intent with practicality.
Common Blind Measuring Mistakes to Avoid
Most fit problems come from predictable, avoidable errors:
- Measuring once instead of three times
- Mixing centimetres and millimetres
- Ignoring window handles or obstructions
- Assuming walls and frames are perfectly square
- Guessing recess depth instead of checking it
Blindsonline supports accurate ordering with a clear fit assurance policy, designed to reduce risk when buying custom blinds.
Measuring for Custom Blinds in South Africa
South African homes often feature older masonry, plastered reveals, and strong sun exposure. These conditions expose even minor measuring errors.
When measuring for custom blinds:
- Expect small inconsistencies in older window frames
- Measure every window individually, even if they appear identical
- Allow extra coverage for heat, glare, and privacy
Custom-made blinds demand precision. Millimetres determine how the blind seals, sits, and performs over time.
Measure Once, Fit Right
Measuring your windows is not difficult, but it does require discipline. Take your time, measure methodically, and follow the correct process for your chosen blind and mount type.
When measurements are accurate, everything else aligns, clean lines, smooth operation, and a result that looks intentional rather than improvised.
Ready to proceed? Revisit the measuring guide or explore Blindsonline’s made-to-measure blinds with confidence.
FAQs
How accurate do window measurements need to be for blinds?
Measurements should be accurate to the nearest millimetre. Even small deviations can affect fit, light control, and operation.
Should I measure in centimetres or millimetres?
Always measure in millimetres. This reduces rounding errors and improves accuracy for custom-made blinds.
Is inside mount (recess) or outside mount (face) better?
Neither is universally better. Inside mounts suit deep, even recesses, while outside mounts offer flexibility and improved coverage.