Runs fully in your browser. Inputs stay on your device. See recent fixes on changelog.
Triangle Calculator
Calculate triangle area, perimeter, and angles.
FreeRuns in browsertriangle calculatortriangle area
Cmd/Ctrl+Enter Primary actionCmd/Ctrl+Shift+L Load sampleCmd/Ctrl+Shift+X Clear/resetCmd/Ctrl+Shift+C Copy result
About Triangle Calculator
Calculate triangle area, perimeter, and angles from three side lengths online for free. Uses Heron's formula for area and the law of cosines for angles. Uses precise mathematical formulas with clear, formatted results. Input validation prevents errors and guides correct usage, ensuring reliable computations every time. Everything runs client-side in your browser for maximum speed and privacy — no data is sent to any server, and no signup is required.
Related tools: Pythagorean Theorem Calculator, Circle Calculator, Area Calculator
How to Use Triangle Calculator
- Fill in the required input fields with your values.
- Click Calculate to run the computation.
- View the results below the form.
Frequently Asked Questions
What is Triangle Calculator?
Calculate triangle area, perimeter, and angles from three side lengths online for free. Uses Heron's formula for area and the law of cosines for angles.
How are calculations performed?
Calculations use precise mathematical formulas implemented in JavaScript. The underlying formulas are well-documented and validated against known reference values to ensure correctness.
Can I use decimal values?
Yes, all input fields accept decimal numbers with full floating-point precision. You can enter values with as many decimal places as you need and the tool will compute accurate results.
Are the formulas used shown?
Where applicable, the tool displays the formula or methodology used so you can verify the computation yourself. This transparency helps you understand and trust the results.
Is Triangle Calculator free to use?
Yes, this calculator is completely free to use. No account or signup is needed, and all computations run locally in your browser without any restrictions.
Is my data safe when using Triangle Calculator?
Absolutely. Every calculation runs locally in your browser. No input data is transmitted to any server, ensuring your numbers stay private.