Geometry & Shapes
Triangle Calculator
Triangle Calculator is a browser-based calculator tool on CalcToolsBase. Free, browser-based Triangle Calculator with instant, clearly-labelled results. No signup, no uploads. To use it, enter your values and view the result directly in your browser — no signup and nothing to install.
From your side a, side b and side c, Triangle Calculator computes the area and perimeter via standard area and perimeter formulas. No accounts, no uploads — just an instant way to find the area and perimeter of the shape.
About this calculator
Triangle Calculator exists to find the area and perimeter of the shape with the least fuss. From your side a, side b and side c it derives the area and perimeter using standard area and perimeter formulas, all on your device. There are no accounts, no adverts in the result, and nothing leaves your browser.
It's aimed at students, designers and DIYers: give it your side a, side b and side c and the area and perimeter comes back clearly labelled, with tidy, easy-to-read numbers. The tool is free, ad-light, and keeps everything in your browser.
How to use
- Enter the length of side a.
- Enter the length of side b.
- Enter the length of side c.
- Press Calculate to find the area and perimeter.
Why use Triangle Calculator
Fast
Calculations run in your browser. No round trip to a server.
Private
Your inputs never leave your device. Nothing is uploaded.
Free
No signup, no paywall, no ads-in-results, no watermarks.
Accurate
Uses standard formulas where applicable; check critical results before relying on them.
Mobile-ready
Optimised for phones, tablets, and desktops alike.
Transparent
Honest disclaimers wherever browser limits or regional rules apply.
Common uses
Triangle for flooring and tiling estimates
Triangle in design and layout work
Triangle when planning a garden bed
Triangle when comparing two shapes
Triangle for craft and woodworking projects
Triangle for everyday area and perimeter maths
Technical notes
Triangle Calculator uses Heron’s formula (or ½·base·height) for area and sums the sides for the perimeter.
Results assume exact, idealised shapes; real-world measurement error is not included.
Results are rounded for display; the underlying calculation keeps full precision.
FAQ
How does it find the area from three sides?
It uses Heron's formula, which finds the area from the three side lengths through the semi-perimeter.
What is the triangle inequality?
Any two sides must add up to more than the third side; otherwise the three lengths cannot form a triangle.
What is the semi-perimeter?
The semi-perimeter is half the perimeter, an intermediate value Heron's formula uses to compute the area.
Does the Triangle Calculator send my data to a server?
No. The Triangle Calculator runs entirely in your browser, so nothing you enter is uploaded, stored, or shared.
Worked example
A triangle with base 10 and height 6 has area = ½ × 10 × 6 = 30.