Similar Triangles Calculator

Find missing sides of similar triangles using proportions.

Triangle 1 - Side a (units)

Triangle 1 - Side b (units)

Triangle 1 - Side c (units)

Triangle 2 - Side a (units)

Formula

a1/a2 = b1/b2 = c1/c2 (k = scale factor)

Similar triangles have equal corresponding angles and proportional sides. The ratio k = a2/a1 is the scale factor.

Examples

3-4-5 scaled to 6-?-?

5-12-13 scaled to 10-?-?

Frequently Asked Questions

What are similar triangles?

Similar triangles have the same shape but different sizes. Their corresponding angles are equal and sides are proportional.

How do I find missing sides of similar triangles?

Find the scale factor k = (known side of T2) / (corresponding side of T1), then multiply T1 sides by k.

About this Calculator

Find missing sides of similar triangles using proportions. All calculations are performed in your browser for instant results. Formulas are mathematically exact using JavaScript's built-in Math functions.