Everyday utility

Triangle Calculator

Calculate the area, perimeter, and type of a triangle given three side lengths. Use this Data and utilities tool to enter your numbers, review the result, and understand the key assumptions before making the next decision.

What you get
A focused calculator, clear explanation, common questions, and useful next tools.
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Result
Explanation
Common questions
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How this calculator works
The result depends on the numbers you enter and the assumptions shown below.

Given sides a, b, c: Perimeter = a+b+c. Area (Heron's formula) = √(s(s−a)(s−b)(s−c)) where s = perimeter/2. Triangle validity: each side must be less than the sum of the other two.

Review the inputs carefully and treat the output as an estimate. For decisions involving money, taxes, health, law, or security, compare the result with trusted professional guidance when needed.

Frequently asked questions

What is Heron's formula?

Heron's formula calculates area from three sides without needing to know the height. Area = √(s(s−a)(s−b)(s−c)) where s = (a+b+c)/2 (semi-perimeter).