CalcCommons
Construction & Measurement

Area Calculator

Calculate the area of six geometric shapes with conversions to common square units.

01 · Set it up

Your inputs

Choose a quick value or enter your own. Example inputs are filled in to get you started.

The main area result uses this unit squared. Other unit conversions are also shown.
02 · A little clarityEXAMPLE RESULT

Enter your measurements and calculate.

Calculated in your browser. Shared links include your entered values; only share information you intend to make public.

How to use

Choose a geometric shape and length unit. Only dimensions needed for that shape are shown. For circles, choose radius, diameter, or circumference and enter that one measurement. For a trapezoid, enter both parallel bases and the perpendicular height.

For related tasks, try the Square Footage Calculator.

Formula & how it works

Rectangle/parallelogram: A = bh. Square: A = s². Triangle: A = bh/2. Circle: A = πr² = πd²/4 = C²/(4π), where r is radius, d is diameter, and C is circumference. Trapezoid: A = (a + b)h/2.

Length12 ftWidth10 ftArea120 ft²
Example inputs · rectangle. Schematic, not to scale.

Worked example

Example 1

A trapezoid with bases 8 m and 12 m and height 5 m has area (8 + 12) × 5/2 = 50 m².

Assumptions & practical notes

For circles, select radius, diameter, or circumference to match your measurement. A sloping side is not the perpendicular height of a triangle or parallelogram.

This geometry tool evaluates one shape; use Square Footage for multiple rooms and price estimates.

See our calculation methodology for unit definitions and testing practices.

Results are estimates for planning purposes. Verify measurements, product specifications, and applicable building codes before purchasing materials or starting work.

Frequently asked questions

Why are conversion factors squared?

Area has two length dimensions. Since 1 ft = 0.3048 m, 1 ft² = 0.3048² m².

How can I measure an irregular area?

Divide it into simple shapes, calculate each, and add their areas without double-counting overlap.

Can I calculate circle area from circumference?

Yes. Select Circle, then Circumference. The calculator uses A = C²/(4π). You can also choose radius or diameter.

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