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Square Footage Calculator

Area for rooms, circles, triangles and odd shapes — added together and converted to any unit.

Enter a measurement to see the area in square feet, metres, yards and acres.

I am measuring in

Mix shapes freely — everything is converted before it is added up.

Shape

Length

Width

How many

Shape

Length

Width

How many

Exact calculation. Given your inputs, this is the answer — no estimation involved.

How this calculator works

Each shape uses its own formula, and every measurement is converted to feet before anything is added. That means you can measure one room in inches and a yard in metres and still get a correct total.

Conversions are exact by definition: an inch is exactly 0.0254 metres, so a foot is exactly 0.3048 metres. Nothing here uses an approximation like 3.28 feet per metre.

For an L-shaped or irregular space, split it into rectangles and add them as separate areas. That is what a surveyor does, and it is more reliable than trying to find one formula for the whole shape.

The formula

Exactly what happens to your numbers, step by step.

The four shapes

rectangle  A = length × width
circle     A = π × (diameter ÷ 2)²
triangle   A = ½ × base × height
trapezoid  A = ½ × (side A + side B) × height

Unit conversions

1 sq ft  = 144 sq in
1 sq yd  = 9 sq ft
1 sq m   = 10.7639 sq ft
1 acre   = 43,560 sq ft

A worked example

An L-shaped living area split into two rectangles, plus a circular rug alcove.

What you enter

Main area: 18 ft × 14 ft
Extension: 8 ft × 10 ft
Alcove: 6 ft diameter circle

The working

Main area: 252 sq ft
Extension: 80 sq ft
Alcove: π × 3² = 28.3 sq ft
Total: 360.3 sq ft

360.3 square feet — about 33.5 square metres

Splitting an L-shape into rectangles is not a compromise; it is the correct method. Buying flooring for this room means adding a waste factor on top — the Flooring Calculator handles that.

Assumptions

Every result here rests on these. Change your inputs and the result changes with them.

Measurements are of flat, two-dimensional area.
Circles are measured by diameter, not radius, because a diameter is what you can actually measure across a room.
Quantities multiply an identical shape, for repeated rooms or panels.

Questions people ask

How do I calculate the square footage of an L-shaped room?

Split it into two rectangles at the corner, measure each, and add them. This calculator lets you add as many areas as you need and totals them for you.

How do I convert square feet to square metres?

Multiply by 0.0929, or divide by 10.7639. Both come from the exact definition that one foot is 0.3048 metres.

Does square footage include closets and hallways?

For flooring and paint, measure exactly what you will cover. For real estate listings, conventions vary by region and typically measure to the interior walls of finished, heated space.

Sources and review

This calculator uses standard arithmetic with no external rules or published rates, so there is nothing to cite beyond the formulas shown above.

Methodology version 1.0.0 · Last reviewed September 6, 2026