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Geometry calculator

Calculate areas, perimeters and volumes for defined shapes in one tool, rejecting invalid triangles.

Calculations stay in this browser, without requests carrying your entries or automatic storage. The bounded synchronous calculation has no background progress or cancellation task.

All dimensions use the selected unit; changing that label does not convert entered numbers. Dimensions must be positive and at most 1000000000000, with at most 13 whole digits including leading zeros and 6 fractional digits. Enter a radius, not a diameter, for circles, cylinders and spheres. A triangle requires three sides with the sum of the two shorter sides strictly larger than the longest. No degenerate triangle is accepted.

Triangle validation and all four Heron factors use exact scaled integers before the square root, preserving thin valid triangles. Square roots, π and displayed geometric results are binary64 approximations shown to at most 12 significant digits. π = 3.141592653589793. These limits are not a promise of exact geometric measurements.

How to use

Choose a shape and shared length unit, then enter its dimensions. Use the radius for circles, cylinders and spheres, and all three sides for a triangle. Calculate, inspect squared area or cubed volume units, then download the report.

Try an example

A 3×4 m rectangle has perimeter 14 m and area 12 m². A 3–4–5 m triangle has perimeter 12 m and area 6 m². A 3×4×5 m cuboid has surface area 94 m² and volume 60 m³.

Support & limits

Rectangle: P=2(a+b), A=ab. Circle: P=2πr, A=πr². Cuboid: S=2(ab+ac+bc), V=abc. Right cylinder: S=2πr(r+h), V=πr²h. Sphere: S=4πr², V=4πr³/3. For sorted triangle sides x≥y≥z, require y+z>x; area is sqrt((x+y+z)(z−x+y)(z+x−y)(x+y−z))/4. Validation and factors use scaled BigInt values before approximation, preserving thin triangles against floating-point cancellation. π=3.141592653589793; square roots and displayed results are binary64 approximations with at most 12 significant digits. Selecting a unit changes the label, not the numbers; mixed units and composite shapes are unsupported.

Common questions

Are sides accepted when they satisfy equality instead of the triangle inequality?

No. Degenerate or invalid triangles produce an explicit error, rather than a zero area presented as a successful nondegenerate shape.

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