▣ CALCULATORS Updated July 25, 2026

Triangle Calculator

Area, perimeter, and angles of any triangle.

Side a
Side b
Side c
Result
Ad space · belowTool · horizontal

How it works

With three sides the tool uses Heron's formula, then derives each angle with the law of cosines. It also checks the triangle inequality before calculating.

Related tools

◔Age Calculator◑BMI Calculator◒Fraction Calculator

Frequently asked questions

What is Heron's formula?

Area = √(s(s−a)(s−b)(s−c)) where s is half the perimeter.

Why do I get an error?

Each side must be shorter than the sum of the other two, otherwise no triangle exists.

Comments

Comments aren't enabled yet. When you're ready, this is where a service like Giscus, Disqus, or a custom form would go — the slot is already reserved on every tool page.