Blind Size Calculator

Written by Great Medico

Updated September 25, 2026 •2 min read

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If your goal is to turn three-point window measurements into an inside- or outside-mount blind order size, you usually do not need a long worksheet—you need the right relationship and sensible inputs. The Blind Size Calculator applies that relationship directly and shows the result in a form that is easy to compare with another scenario or a manual check.

What this calculator does

The calculator’s primary output is inside-mount blind size. It also exposes useful supporting values such as Width basis, Height basis. Its scope is deliberately narrow: it uses the fields shown for Blind Size and does not silently add outside prices, specifications, measurements, or assumptions that are not present on the page. Where the page uses a chart, threshold, lookup, or heuristic rather than a continuous physical equation, the result should be read as a category or recommendation produced by that current model.

How to use it

Enter Mount type, Hanging style, Width top, then complete Width middle, Width bottom, Height left, Height center, Height right. Measure dimensions and read product labels where possible. For cost estimates, use the tariff or unit price you actually pay; for quantity estimates, round to purchasable package sizes only after reviewing the calculator’s unrounded result.

How the calculation works

Inside mount uses the smallest of three measured widths and the longest of three heights, with a small sill adjustment for clear hanging. Outside mount uses the largest measurements and adds the current width/height allowances.

Example

For example—Mount type (Inside mount); Hanging style (Touch window sill); Width top (36 in)—the calculator returns 35.8 × 60.2 in for inside-mount blind size. Change one of those inputs and the result should move in the direction implied by the formula or lookup above. That is a useful way to catch a unit mistake or an unrealistic assumption before relying on the estimate.

How to interpret the result

For the Blind Size Calculator, read the inside-mount blind size as a planning estimate under the prices, dimensions, usage, or product assumptions entered. The most useful insight is often how the result changes when one realistic assumption changes. The Blind Size Calculator result should also pass a rough magnitude check. If it is ten or one hundred times larger than expected, recheck units and whether a value was entered as a total versus a per-unit amount.

Limitations and notes

For the Blind Size Calculator, this is a compact planning model. Real prices, tariffs, product efficiency, waste, taxes, local standards, installation conditions, and manufacturer instructions can change the final cost or quantity. Use current local inputs and round practical purchases in the direction that avoids shortage when appropriate.