What is Heron's formula?

Heron's formula computes triangle area from all three side lengths (a, b, c). First compute the semi-perimeter s = (a+b+c)/2, then Area = √(s(s−a)(s−b)(s−c)). No angles are needed.

What is the SAS method?

SAS stands for Side-Angle-Side. When you know two sides and the angle between them, Area = (1/2) × a × b × sin(C), where C is the included angle in degrees.

What units does the result use?

The result is in the square of whatever unit you enter. If you enter sides in meters, the area is in square meters (m²). The tool does not convert units.

What makes a valid triangle?

For three sides to form a triangle, each side must be less than the sum of the other two (triangle inequality). The tool will warn you if the entered sides cannot form a valid triangle.

Can I use decimal values?

Yes. All inputs accept decimal values such as 3.5 or 12.75. Results are rounded to six significant figures for readability.

Is the included angle measured in degrees or radians?

The SAS method accepts degrees (0–180). The tool converts to radians internally before applying the sine function.

Triangle Area Calculator

Calculate triangle area using base & height, three sides (Heron's formula), or two sides with included angle (SAS).

Enter Measurements

Base

Height

Result

Area — square units

Enter values on the left to see the formula and result.

Summary

This tool calculates the area of any triangle using three methods: base and height, Heron's formula (three sides), or the SAS method (two sides and the included angle). Each calculation displays the exact formula used so you can follow the math step by step.

How it works

Select a calculation method: Base & Height, Three Sides (Heron's), or SAS.
Enter the required measurements in the input fields.
The area is calculated instantly as you type.
The formula and substituted values are shown below the result.
Click "Copy Result" to copy the numeric answer to your clipboard.

Use cases

Calculate land or floor area from surveyed triangle dimensions.
Solve geometry homework with step-by-step formula display.
Find triangle area when only three side lengths are known.
Use the SAS method when two sides and the angle between them are measured.
Verify hand-calculated triangle areas quickly.
Support architectural or engineering layout calculations.
Teach or learn the three standard triangle area formulas.
Cross-check results from different measurement methods.

Frequently Asked Questions

Last updated: 2026-05-28 · Reviewed by Nham Vu