Geometry Calculator

Pick a shape, enter its dimensions, and see the area/perimeter or volume/surface area update as you type — with the formula worked out step by step underneath.

How to use this calculator

Choose 2D or 3D, pick a shape, then fill in its dimensions — results and the worked formula appear underneath as soon as there's enough to calculate. All results are in whatever unit you entered (squared for area/surface area, cubed for volume).

2D shapes Square, rectangle, triangle, circle, parallelogram, trapezoid, regular polygon, and ellipse - each gives you area and perimeter (circumference, for a circle).
3D shapes Cube, rectangular prism, sphere, cylinder, cone, square pyramid, and triangular prism - each gives you volume and surface area.
Shape diagram 2D shapes are drawn to actual scale from what you enter. 3D shapes have no flat "true size" to draw, so those are a fixed-angle isometric illustration instead - the proportions do reflect your dimensions, but it's a schematic 3/4 view, not a rotatable 3D scene.
Triangle & triangular prism Enter all three sides of the triangle - area is computed with Heron's formula. If the three lengths can't actually form a triangle (one side longer than the other two combined), you'll get an error instead of a nonsense result.
Ellipse perimeter There's no exact formula for an ellipse's perimeter, so that one uses a well-known close approximation (Ramanujan's) - everything else on this page is exact.
Reading the formula line Each result shows its working as a chain: the general formula, then the same formula with your numbers substituted in, then the final answer - e.g. for a circle of radius 5, Area = πr² = π × 5² = 78.5398.