Triangular Prism Calculator

A triangular prism is the solid you get by taking a triangle and stretching it straight back to a given length, the shape of a Toblerone bar, a ridge tent, a roof truss or a glass prism that splits light, and this calculator works out its volume and surface area in one step. Enter the three sides of the triangular cross-section and the length of the prism, and it returns the volume, the total surface area and the area of the triangular end, updating as you type. The volume follows the rule that applies to every prism: find the area of the cross-section and multiply by the length. The clever part is the cross-section, because giving three side lengths is the most flexible way to describe a triangle, and the calculator finds its area using Heron's formula, which needs nothing more than those three sides, so you do not have to know the triangle's height. The surface area then adds the two triangular ends to the three rectangular faces that wrap around the prism, which together come to twice the triangle area plus the triangle's perimeter times the length. That makes this tool genuinely useful for maths students learning solid geometry and checking homework, for builders and roofers working out the volume and cladding of a ridge or a wedge, for anyone calculating the capacity of a trough or a hopper with a triangular section, and for design and packaging work. Because the results update live, you can change any side or the length and immediately see how the volume and surface area respond, which builds a real feel for how prisms scale. The formulas and a worked example are explained clearly below.

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The three sides must form a valid triangle (each side less than the sum of the other two).