8 free online calculators with step-by-step solutions
Pick the right tool for your problem — 2D shapes, 3D solids, proofs, or composite figures.
Start with these essential proofs & theorems calculators
Proofs are where geometry stops being arithmetic and becomes logic — every step justified by a definition, postulate, theorem, or earlier result. The calculators below assist with the mechanical side: checking SSS / SAS / ASA / AAS / HL congruence between two triangles, verifying AA / SAS / SSS similarity ratios, applying the Basic Proportionality Theorem (BPT) when a line parallel to one side cuts the other two, and testing inscribed-angle and angle-sum relationships. The goal is not to replace your reasoning but to confirm a candidate proof step or surface the postulate Google's search will tell you applies. For two-column proof tutorials and worked examples, see our /how-to-write-two-column-geometry-proofs/ guide.
This collection has 8 geometry proof calculators: 4 are tagged Most Popular, 3 are supporting tools, and 1 are advanced calculators for derivations and proofs. The most-used tools include Pythagorean Theorem Calculator, Congruent Triangles with Parallel Lines Calculator, Similar Triangles with Parallel Lines Calculator.
1 of these calculators support AI Vision: upload a photo of your problem (handwritten, textbook, or whiteboard) and the AI returns the full step-by-step solution. Vision-enabled tools in this category include Geometric Proofs Calculator.