Roller blind measurement guide
Estimate outside-mount order dimensions with editable overlaps.
Back to calculator ↑Measure and prepare
Measure width and height at several points. Check obstructions and bracket space. The example treats three openings as equal; calculate different sizes separately.
Measure the opening at top, middle and bottom, and height at left, centre and right. Note handles, existing curtain hardware and available wall space for brackets. The starting setup is an outside mount, so enter side and vertical overlaps according to the coverage you need and the chosen seller’s measuring rules.
How the estimate works
Order width equals opening width plus both side allowances. Order drop equals opening height plus combined top/bottom allowance. One blind serves each opening. Enter a model’s maximum order width once known to check whether it fits.
For the example, 1.5 m opening width plus 0.05 m on each side gives 1.60 m order width. A 1.8 m opening plus 0.1 m combined vertical allowance gives 1.90 m drop. Three equal openings need three blinds. If this order width exceeds the selected model’s maximum, choose another model or design multiple blinds.
Check the order
Ask whether order width means bracket-to-bracket or fabric width; fabric is often narrower. Check outside/inside mount instructions and model-specific maximum width before purchase.
Tell the seller this is an outside mount. “Blind width” may mean bracket-to-bracket rather than fabric width, and the narrower fabric can leave side light gaps. Confirm roll direction, control or motor position, suitable fixing substrate and any cord-safety requirements for the chosen product.
Limits of the estimate
Default overlaps are illustrative, not universal. Inside mounts require the seller’s deduction method.
The 0.05 m side overlap is editable and does not guarantee full blackout or bracket clearance. Inside mounts need measurements at several points and the manufacturer’s own deductions. Calculate unlike openings separately so the order does not mistakenly repeat one size for every window. For inward-opening windows, test the planned blind position with the sash open. The roller and brackets must clear the frame and handle during use.
Common questions
Is fabric width the order width?
Often no; check the chosen mechanism specification.
Can I use this for inside mount?
Not directly; use the seller’s inside-mount measuring rules.
What if width exceeds the maximum?
Choose another product or divide into multiple blinds and account for gaps.
Sources and calculation guidance
Check these against your chosen product’s label and instructions.