Triangle Calculator
Area, perimeter, angles and height from sides or angles.
Area
20.333163cm²
Perimeter
21cm
Angle A
46.567°
Angle B
57.91°
Angle C
75.522°
Height on a
6.777721cm
ShowHide the working
- 1Semi-perimeter s = (6 + 7 + 8) ÷ 2 = 10.5
- 2Heron: area = √(s(s−a)(s−b)(s−c)) = 20.333163
- 3Angles from the cosine rule
Formula
area = √(s(s−a)(s−b)(s−c)), s = (a+b+c)/2How it works
Heron's formula gives the area from three sides alone; the cosine rule then gives every angle.
Example
Sides 6, 7 and 8 give an area of 20.33 and angles of 46.6°, 57.9° and 75.5°.
About the Triangle Calculator
Area, perimeter, angles and height from sides or angles. It sits in the Geometry section of NWS Calc, a free collection of calculators that run entirely in your browser. There is no signup, no paywall and no tracking — open the page, enter your numbers, get an answer.
Frequently asked questions
- Is the Triangle Calculator free to use?
- Yes. Every calculator on NWS Calc is completely free, with no signup, no usage limits and no ads.
- Does my data leave my device?
- No. The Triangle Calculator runs entirely in your browser using JavaScript. Nothing you type is uploaded, logged or stored on a server.
- Can I use the Triangle Calculator on my phone?
- Yes. The page is fully responsive and works in any modern mobile or desktop browser — there is nothing to install.
- What else is in Geometry?
- Area, perimeter, volume and surface area for every common shape. You can browse the full Geometry category for related calculators.