About Sqft Calculators

A free set of square footage calculators built to be fast, accurate and free of the clutter that usually surrounds tools like these.

What this site is for

Square footage comes up constantly — buying a house, ordering flooring, sizing an air conditioner, quoting a roof — and the maths is genuinely simple. What is not simple is knowing which formula applies, what to include, and which convention the person asking is using.

So this site is two things: sixteen calculators that do the arithmetic, and fourteen guides that explain the parts the arithmetic does not cover.

How the numbers are verified

Every calculation on the site runs through a single shared module, so there is one implementation of each conversion rather than sixteen. That module is checked against known reference values:

• 1 acre = 43,560 sq ft (exact, from 66 ft × 660 ft)
• 1 sq m = 10.7639104 sq ft (derived from the international foot, 0.3048 m exactly)
• 1 sq yd = 9 sq ft, 1 sq ft = 144 sq in
• A circle 10 ft in diameter = 78.5398 sq ft
• A 6/12 roof pitch multiplier = 1.1180

Where a figure is a trade convention rather than a physical constant — 350 sq ft of paint coverage per gallon, 20 BTU per square foot for cooling, a 10% flooring waste allowance — it is stated as such on the page, with the reasoning, so you can adjust it.

Estimates, not guarantees

These tools are for planning. For anything with legal or financial consequence — a property listing, an appraisal, a permit application, a boundary dispute, or a large materials order — verify measurements on site and consult the relevant professional. A calculator cannot see your building.

Privacy and performance

Every calculation runs in your browser. Nothing you type is transmitted, logged or stored anywhere. There are no accounts and no sign-up.

The site is built as static HTML with no framework running in the browser. Content pages ship no JavaScript at all; calculator pages ship a few kilobytes. That is a deliberate choice — a tool you use for thirty seconds should not take five seconds to load. Full details are in the privacy policy.

Corrections and requests

If you find an error, or there is a calculator you need that is not here, please get in touch. Corrections are genuinely welcome — a wrong conversion factor on a site like this propagates into real material orders.