Square Footage Calculator

Guides and articles

Guides to measuring rooms, lots and materials accurately — how to handle awkward shapes, what to include, and where square-footage figures usually go wrong.

What these guides cover

The calculators on this site answer a narrow question well: given these measurements, what is the area? These articles cover everything around that question — how to take measurements you can trust, which surfaces to include, what to do with a room that is not a rectangle, and how to turn a square footage figure into an order that arrives complete.

Most bad square footage figures come from four places, and none of them is the arithmetic. Mixing units — feet on one side, inches on the other — is the biggest, and it produces answers twelve times out. Measuring to the wrong surface comes next: interior room measurements and exterior building measurements differ by the thickness of every wall. Skipping the waste factor leaves a tiling job a box short on its last afternoon. And rounding before the final step compounds through every conversion afterwards.

Where to start

If you are measuring a space for the first time, start with the practical guide to calculating square footage, which walks through feet and inches, awkward shapes, whole houses, walls, roofs and yards in one place. From there, each shape page carries the measuring detail specific to that geometry, and the FAQ answers the questions that come up most often. If a figure arrives in the wrong unit, the unit converters turn it into the one you work in.

For the underlying math, the square footage formula for every shape is the hub, with dedicated walk-throughs for a triangle and a circle. And if a figure still feels abstract, how big is 1,000 square feet puts the common sizes next to things you can picture.