Similar Triangles Calculator

Enter a matching side pair to scale another triangle, or compare two complete side sets with an SSS similarity check and transparent proportional ratios.

Triangle 1 side a

Triangle 2 matching side a′

Triangle 1 side b

Triangle 1 side c

Scale factor = 2Corresponding side lengths scale linearly; areas scale by k².

—Triangle 2 side b′

—Triangle 2 side c′

—Perimeter ratio

—Area ratio

Similarity calculations assume you paired corresponding sides correctly. SSS mode checks proportional side sets; it does not infer correspondence from a diagram.

Connected geometry workflow

v10.86 connects broad area, perimeter, volume and surface-area heads with triangle, circle, polygon, coordinate-center and similarity specialists without replacing the established geometry engines.

Use consistent measurements and valid geometric assumptions

Keep linear inputs in a consistent unit, verify that side lengths or coordinate points can form the stated shape, and treat sketches as explanatory unless explicitly marked to scale. Coordinate formulas can become unstable for nearly degenerate shapes, so invalid or nearly collinear inputs are rejected rather than silently returning misleading values.

How to use this Similar Triangles Calculator

Find a scale factor, missing corresponding sides, perimeter ratio, and area ratio for similar triangles, or check SSS similarity.

Enter, paste, upload, or choose the inputs shown in the tool above.
Adjust the available options for the result you need.
Review the output before copying, downloading, or using it elsewhere.

What this tool does

Enter a matching side pair to scale another triangle, or compare two complete side sets with an SSS similarity check and transparent proportional ratios.

Practical tips and limits

Review the inputs and result before using the output elsewhere. Keep the original data when the operation changes or replaces content.