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Triangle Calculator

Solve sides, angles, area, and perimeter from SSS, SAS, ASA, or right-triangle inputs.

Clear formulas
Educational steps
Detail breakdown

Triangle modes cover law of cosines/sines and right-triangle Pythagorean cases.

Limitation: Educational geometry.

Jump to calculator · Sources & review

How to Use the Triangle Calculator

Triangle modes cover law of cosines/sines and right-triangle Pythagorean cases.

1

Open the Triangle calculator and read field labels.

Match the mode

Educational geometry.

What It Calculates

Triangle modes cover law of cosines/sines and right-triangle Pythagorean cases.

Worked Examples

SSS 3-4-5

Inputs

mode:sss
sideA:3
sideB:4
sideC:5

Result

Area = 6

Right 3-4-5 triangle; area 6.

Right legs 3 & 4

Inputs

mode:right
legA:3
legB:4

Result

c = 5

Hypotenuse √(9+16) = 5.

SAS sides 5,7 angle 60°

Inputs

mode:sas
sideA:5
sideB:7
angleC:60

Result

Area computed

Uses law of cosines for third side.

Check your mode

Educational geometry.

Frequently Asked Questions

Yes. Results keep the precision shown on the page unless the engine requires integers.

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Formulas

Standard definitions with assumptions noted below.

Formula

A ​=​ √​(​s​(​s−a​)​​(​s−b​)​​(​s−c​)​​)​

Scientific Background

Standard geometry definitions with assumptions stated on-page. Educational only—not professional certification.

Sources & review

Triangle Calculator documents the references behind its formulas and assumptions. Always treat results as educational estimates, not personalized professional advice.

Last reviewed

July 22, 2026

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