Calculators
Triangle Calculator
Calculate triangle perimeter and area from three side lengths locally in your browser.
Enter three side lengths from 0 (exclusive) to 1000000000 to see the perimeter (a + b + c), area (Heron's formula), side type, and angle type. The calculation runs locally in your browser; your values are not uploaded or stored.
Find triangle measurements without uploading anything.
Enter three side lengths from 0 (exclusive) to 1000000000 to see the perimeter, area, side type, and angle type. Everything runs locally in your browser, so your values are not uploaded or stored.
Frequently Asked Questions
Everything you need to know about this tool, how it works, and privacy.
What does the triangle calculator show?
Enter three side lengths from 0 (exclusive) to 1000000000. The calculator returns the perimeter (a + b + c), the area with Heron formula, the side type (equilateral, isosceles, or scalene), and the angle type (acute, right, or obtuse). For example, sides 3, 4, and 5 give perimeter 12, area 6, scalene side type, and right angle type.
Which formulas does the triangle calculator use?
It uses perimeter = a + b + c and area = square root of s(s-a)(s-b)(s-c), where s is half the perimeter. Side type compares the three lengths, and angle type compares the squares of the sorted sides: x squared + y squared versus z squared.
Which inputs are accepted?
Enter three numbers greater than zero through 1000000000. Decimal values are accepted. Zero, negative numbers, non-numeric text, values above the limit, and triples that violate the triangle inequality show a clear error instead of a result.
Do my numbers stay private?
Yes. The calculation and copy action run locally in your browser. CodeASystem does not upload or store the values you enter.