What is Heron's formula?

Heron's formula computes triangle area from three side lengths: Area = sqrt(s(s-a)(s-b)(s-c)) where s = (a+b+c)/2 is the semi-perimeter.

What is the circumradius of a triangle?

The circumradius (R) is the radius of the circle that passes through all three vertices: R = (a × b × c) / (4 × Area). The inradius (r) is the radius of the inscribed circle: r = Area / s.

/ student tools

Triangle Calculator

Live

Enter any two sides - the third will be calculated

Side a (leg)

Side b (leg)

Side c (hyp)

Side a

3.0000

Side b

4.0000

Hypotenuse c

5.0000

Angle A

36.87°

Angle B

53.13°

Angle C

90.00°

Area

6.0000

Perimeter

12.0000

Inradius

1.0000

Circumradius

2.5000

a² + b² = c² · 3.0000² + 4.0000² = 5.0000²

Privacy First: Your files are processed securely. Whenever possible, processing happens in your browser and files are never stored on our servers.

Three triangle solvers: Pythagorean theorem for right triangles, Law of Sines/Cosines for any triangle, and area by base-height/Heron/SAS. Shows perimeter, inradius, circumradius, and type.

How to Use

1Select a tab: Right Triangle, Any Triangle, or Area Calculator
2Right Triangle: enter any 2 of the 3 sides - the missing side, both angles, and area are calculated
3Any Triangle: select a known combination (SSS, SAS, ASA, AAS) and enter the known values
4Click Solve - all unknown sides, angles, perimeter, area, inradius, and circumradius are shown
5Area Calculator: choose a method (base-height, Heron, or SAS) and enter the required measurements

Features

3 solvers: Right triangle (Pythagorean), Any triangle (Law of Sines/Cosines), Area
SSS, SAS, ASA, AAS triangle configurations
3 area methods: base-height, Heron's formula, SAS
Perimeter, area, inradius, circumradius
Triangle type classification (equilateral/isosceles/scalene/right/acute/obtuse)
100% browser-based

Triangle Calculator

How to Use

Features

Frequently Asked Questions

/ related tools

Community Feedback

Reviews

Rate & Review

/ share this tool