Square Footage Calculator

Calculate square footage for rectangles, squares, circles, triangles and known areas. Add several labelled rooms, measure in feet and inches, feet, yards, metres, centimetres or millimetres, add a waste allowance, and get totals in sq ft, sq yd and m².

Calculators Runs client-side Free to use

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About the Square Footage Calculator

Square Footage Calculator works out the floor area of one room or a whole project. Add as many labelled areas as you need, choose a shape for each — rectangle, square, circle, triangle, or a custom area you already know — and enter its measurements in feet and inches, feet, yards, metres, centimetres or millimetres. Each area and the combined total are shown in square feet, square yards and square metres, using exact conversion factors.

An optional waste allowance adds a percentage for cutting and offcuts when you order flooring, carpet or other materials. The results always show the measured area and the area including waste separately, so you never confuse the two. The calculation breakdown lists the formula used for each area, and you can copy or download a readable summary. Missing, zero, negative, malformed and implausibly large measurements are rejected with a clear message naming the area.

How to use

Choose the unit you measured in.
For each room or area, enter a label, pick a shape and type its measurements.
Click Add another area for more rooms, and enter a waste percentage if you need one.
Click Calculate to see each area and the total in sq ft, sq yd and m².
Copy or download the summary for your records or supplier.

Key features

Rectangle, square, circle, triangle and custom (known) area shapes.
Feet + inches, feet, yards, metres, centimetres and millimetres.
Up to 50 labelled areas with a combined total.
Results in square feet, square yards and square metres.
Optional waste allowance, shown separately from the measured area.
Formula breakdown, copy and download summary, and full Reset.

Best practices

Measure each wall at floor level and round up to the nearest inch or centimetre.
Split L-shaped or irregular rooms into rectangles and add them as separate areas.
Subtract fixed features (such as a kitchen island) by measuring the remaining areas separately.
Use a waste allowance of around 5–15% for flooring, more for diagonal layouts.
Double-check the unit before entering numbers.

Benefits

Accurate area totals for flooring, carpet, paint and property listings.
Instant conversion between imperial and metric units.
Clear separation of measured area and ordering quantity.
Private and free — no sign-up or uploads.

Frequently asked questions

How do I calculate square footage?

For a rectangle, multiply length by width in feet. For a circle, use π × (diameter ÷ 2)²; for a triangle, ½ × base × height. Add the areas of all rooms for the total.

How do I enter feet and inches?

Choose “feet + inches” as the unit. Each measurement then has a feet box and an inches box; inches must be less than 12. For 12 ft 6 in, enter 12 and 6.

What does the waste allowance do?

It adds a percentage on top of the measured area to cover cuts, offcuts and mistakes when ordering materials. The measured area and the area including waste are shown separately.

How do I convert square feet to square metres?

Multiply square feet by 0.09290304, or divide square metres by that number. The calculator shows every result in sq ft, sq yd and m² automatically.

What is a custom area?

Use it when you already know an area, such as a figure from a floor plan. It is entered in square units of the chosen measurement unit (square feet when using feet + inches).

Why was my measurement rejected?

Measurements must be positive numbers. Zero, negative, text, malformed values and dimensions over 5,000 m (about 16,404 ft) are rejected, and the error names the area and field to fix.

Is my data saved or uploaded?

No. Every calculation runs in your browser. Nothing you type is sent to a server or saved in browser storage, and Reset clears it from the page.