Math
Area Calculator
Use the area calculator for common classroom and everyday shapes. Pick a shape, enter its dimensions, and see the formula substitution.
Area
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- Formula used
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Student quick launch
Grade planning, algebra checks, and formulas students reach for most.
Study path
Use this calculator with
Follow these when you want the formula behind the answer, a short lesson, or nearby tools in the same topic.
What the area calculator solves
Use the area calculator for common classroom and everyday shapes. Pick a shape, enter its dimensions, and see the formula substitution.
Formula
How to use it
- Choose the shape.
- Enter the dimensions shown for that shape.
- Use the formula row to check your substitution.
How to read the answer
Area measures the two-dimensional space inside the shape, so answers are in square units.
Common mistakes and edge cases
- Use height perpendicular to the base, not a slanted side.
- Remember to divide triangle area by 2.
- Circle area uses radius, not diameter.
Worked examples
Rectangle area
Area
96
Circle area
Area
78.5398
Frequently asked questions
What units should I use?+
Use any length unit, but keep all dimensions in the same unit. The answer will be in square units.
Why does triangle area divide by 2?+
A triangle is half of a parallelogram with the same base and height.
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Last updated: May 8, 2026