MATH

Triangle Calculator

Estimate triangle from side a, side b, side c with the Triangle Calculator.

Which measurements are known?Choose the three measurements you know. Angles can be entered in degrees or radians.

4 options

Side a

Side b

Side c

TRIANGLE6 m²

SSS · three sides: Solves SSS, SAS, ASA, or AAS triangles with the laws of cosines and sines, then reports every side, angle, area, and perimeter.

Side a: 3
Side b: 4
Side c: 5
Angle A: 36.86989765°
Angle B: 53.13010235°
Angle C: 90°
Area: 6
Perimeter: 12

Result unitEstimate based on the values shown

MethodSolves SSS, SAS, ASA, or AAS triangles with the laws of cosines and sines, then reports every side, angle, area, and perimeter.

Before you use the result

The result depends on the entered values, selected mode, and displayed mathematical assumptions.

EDITORIAL NOTES

Using the Triangle Calculator responsibly

Page-specific guidance based on this calculator’s implemented method, inputs, and known limits.

What this result is useful for

Triangle calculations depend on which sides and angles are known. The selected workflow applies the corresponding geometric relationship and checks whether the supplied measurements can form a valid triangle.

Assumptions and limits

Angles and lengths must use the displayed units, interior angles sum to 180 degrees, and side lengths must satisfy the triangle inequality. Rounded measurements can produce small discrepancies in a solved angle or side.

How to check the result

Check that the longest side is opposite the largest angle and that all solved sides are positive. Recalculate with an independent relationship, such as the angle sum, Pythagorean theorem for a right triangle, or a law of sines/cosines check.

CALCULATOR GUIDE

How to use the Triangle Calculator

Estimate triangle from side a, side b, side c with the Triangle Calculator. It includes SSS · three sides, SAS · two sides and included angle, ASA · two angles and included side, AAS · two angles and another side workflows, so choose the one that matches the values you actually know. Use it to check the arithmetic while keeping the displayed method and entered values with your work.

Step by step

For the Triangle example, select SSS · three sides and enter side a, side b, side c. Keep each value in the unit displayed beside its field.
Review the selected Triangle workflow and inputs, then read triangle in the result panel.
Change one Triangle assumption at a time to compare scenarios. Use Reset to restore this tool's worked example values.

How the calculation works

Solves SSS, SAS, ASA, or AAS triangles with the laws of cosines and sines, then reports every side, angle, area, and perimeter.

Worked example

To reproduce the Triangle worked example, reset the calculator. Select the SSS · three sides workflow. Use side a 3 m; side b 4 m; side c 5 m. The result is triangle of 6 m². SSS · three sides: Solves SSS, SAS, ASA, or AAS triangles with the laws of cosines and sines, then reports every side, angle, area, and perimeter. Review the displayed units before comparing the result.

Understanding the result

The Triangle reports triangle. Use it to check the arithmetic while keeping the displayed method and entered values with your work. The result depends on the entered values, selected mode, and displayed mathematical assumptions.

How to check the answer

Check the Triangle answer by substituting triangle back into the stated relationship. Test a simple value such as zero, one, or an equal pair, then confirm that sign, scale, units, and rounding match Solves SSS, SAS, ASA, or AAS triangles with the laws of cosines and sines, then reports every side, angle, area, and perimeter.

Common questions

What does the Triangle calculate?

Estimate triangle from side a, side b, side c with the Triangle Calculator.

Which inputs does the Triangle example use?

The worked example uses side a, side b, side c in the SSS · three sides workflow. Other workflows can show different fields. Keep the chosen workflow and units with the result when comparing calculations.

Is the Triangle result exact?

The result depends on the entered values, selected mode, and displayed mathematical assumptions. Recheck side a, side b, side c and use triangle only for a decision where that level of precision is appropriate.

INTERPRET THE RESULTRead the math guideCheck assumptions, limitations and comparison methods →

KEEP GOING

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