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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, meters, yards and acres.

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

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 meters and still get a correct total.

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

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.

  1. 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

  2. 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

Step by step

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 meters

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.

What this cannot tell you

  • It measures floor area, not usable area. Fitted units, kitchen islands and a staircase footprint all take space that a length-times-width figure counts as floor.
  • Rooms are rarely true rectangles. Older houses in particular are out of square by enough to matter on a flooring order — measure both ends of each wall and use the larger.
  • It cannot tell you what a listing means by square footage. Real estate measurement conventions differ on whether garages, basements, attics and exterior walls count, and the same house can be advertised at very different figures.
  • Sloped ceilings are not handled. Many building codes only count floor area under a minimum ceiling height, which excludes part of a converted loft.

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 meters?

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

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.

How many square feet does a yard of concrete cover?

It depends on the thickness. A cubic yard is 27 cubic feet, so at 4 inches thick it covers 81 square feet, and at 6 inches it covers 54. Measure the area here, then use the concrete calculator to turn it into an order, which adds a 10% allowance by default because ground is never perfectly level and concrete cannot be topped up once it starts to set.

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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

Cite this calculator

For coursework, a resource list or your own site. How every calculator is built and checked is set out on the methodology page.

Citation

Chalk Calculator. (2026, September 20). Square Footage Calculator (Methodology version 1.0.0). https://chalkcalculator.com/square-footage-calculator/

Link to it from your site

<a href="https://chalkcalculator.com/square-footage-calculator/">Square Footage Calculator</a> from Chalk Calculator