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Area Calculator

The defaults compute a rectangle 8 units by 6 units, which is 48 square units. This is one calculator for the three most common area formulas — rectangle (A × B), circle (π times the radius squared, using A as the radius), and triangle (half of base times height) — and results carry the square of whatever length unit you enter: feet in, square feet out.

Area
48
square units
Rect
Drawn to scale
86
Inputs
Shape
×
Both sides in the same unit
Multiply width by height in matching units. Feet times feet gives square feet — mixing feet and inches gives a number that means nothing.
The result is in squared units
Area comes out as the square of whatever length unit you entered — meters in gives square meters out. The calculator itself is unit-agnostic.
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Uses your inputs above
48 area. Want to try a variation?

The math

Reviewed 2026
Formula
rect: a·b; circle: πr²; triangle: ½·b·h

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Example: how area is calculated

Step-by-step with default inputs

Suppose you put the default values into Area Calculator:

Shape
Rectangle
A
8
B
6

Plug those into the formula rect: a·b; circle: πr²; triangle: ½·b·h and the result is:

Area
48

How does the area calculator work?

Area Calculator uses the formula shown in the math card and is computed from first principles. Inputs are validated for sensible ranges; results are computed client-side for instant feedback and do not leave your browser.

Last reviewed July 2, 2026 · Editorial policy

Frequently asked questions

How do you find the area of a circle?

Square the radius and multiply by pi: A = πr². Pick the circle shape and enter the radius in the A field — a radius of 8 gives π × 64 ≈ 201.06 square units. If you measured the diameter, halve it first.

Which number is the base and which is the height for a triangle?

Either order works — area is ½ × base × height and multiplication commutes. What matters is that the height is measured perpendicular to the base, not along a slanted side. A base of 8 and height of 6 gives ½ × 48 = 24 square units.

Why is the answer in square units?

Because the calculator is unit-agnostic: it multiplies whatever lengths you give it, so the result is in the square of that unit. Enter meters and you get square meters; enter feet, square feet. Just don't mix units between the two fields.

How accurate is this area calculator?

The math is deterministic — the same inputs always produce the same output, and the formula is shown above. Accuracy of the answer for your situation depends on how well your inputs match reality and how well the formula models the question.

How do I share my result?

Hit Share at the top of the page. Every input you change is encoded in the URL, so a permalink reproduces exactly what you see. No account needed.