Geometry Calculator

About the geometry calculator

This free geometry calculator works out the key measures of a shape from its dimensions. Choose a shape, fill in the dimensions that shape needs, and it returns:

• 2D shapes — the area and the perimeter.
• 3D shapes — the surface area and the volume.

Everything runs locally in your browser. Nothing is uploaded to a server, and it works offline once the page has loaded.

Supported shapes

2D (area + perimeter)

• Square — side
• Rectangle — width, height
• Triangle — base, height (for the area); add side_a, side_b, side_c to also get the perimeter
• Circle — radius
• Ellipse — radius_a (semi-major), radius_b (semi-minor); perimeter uses Ramanujan's approximation
• Trapezoid — base, top, height; add side_a, side_b (the legs) for the perimeter
• Parallelogram — base, side_a (slant side), height
• Regular polygon — sides (how many), side (edge length)

3D (surface area + volume)

• Cube — side
• Rectangular prism / box — width, height, length
• Sphere — radius
• Cylinder — radius, height
• Cone — radius, height
• Pyramid (square base) — base, height

Units

The calculator is unit-agnostic: enter every dimension in the same unit and the results follow. Lengths come back in that unit, areas in unit² and volumes in unit³ — the JSON marks each value's unit suffix ("", ², ³).

Examples

• Circle, radius = 2 → area 12.566371, perimeter 12.566371
• Rectangle, width = 3, height = 4 → area 12, perimeter 14
• Sphere, radius = 3 → surface area 113.097336, volume 113.097336
• Cylinder, radius = 2, height = 5 → volume 62.831853

How the values are computed

Standard formulas are used throughout — for example circle area is π·r², cylinder volume is π·r²·h, sphere volume is (4/3)·π·r³, and the regular polygon area is (n·s²) / (4·tan(π/n)). Triangle side lengths are checked against the triangle inequality before the perimeter is reported. Results are rounded to six decimal places.

FAQ