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Triangle Calculator

You can solve any triangle from three known pieces, as long as at least one is a side. Common cases are SSS (three sides), SAS (two sides and the included angle), ASA (two angles and the included side), AAS (two angles and a non-included side), and SSA (two sides and a non-includ

Calculators

You can solve any triangle from three known pieces, as long as at least one is a side. Common cases are SSS (three sides), SAS (two sides and the included angle), ASA (two angles and the included side), AAS (two angles and a non-included side), and SSA (two sides and a non-includ

This free Triangle Calculator from KX Toolkit is part of our all-in-one online toolkit. It runs entirely in your browser, so your data never leaves your device for client-side operations. 100% free, forever - no paywall, no credit card, no trial.

How to use the Triangle Calculator

  1. Enter your inputs (date, amount, rate, etc.).
  2. Pick any optional settings (tax mode, country, unit).
  3. Read the result - most calculators update as you type.
  4. Copy the result, or screenshot the breakdown for your records.

What you can do with the Triangle Calculator

  • Quick personal-finance maths before a major purchase.
  • Tax estimates for freelancers and small businesses.
  • Verify a number on an invoice or receipt.
  • Help kids with homework calculations.

Why use KX Toolkit's Triangle Calculator

  • Browser-based: Works on Windows, macOS, Linux, iOS and Android - no install, no extension.
  • Privacy-first: Client-side tools never upload your data; server-side tools delete files right after processing.
  • Mobile-friendly: Full feature parity on phones and tablets - not a stripped-down view.
  • Fast: Optimised for instant feedback. No artificial waiting screens, no email-gated downloads.
  • One hub for everything: 300+ tools across SEO, text, image, PDF, code, color, calculators and more - skip switching between sites.

Tips for the best results

For currency-aware calculators (GST, tax), always confirm the rate matches the jurisdiction on your invoice - rates change yearly.

Related Calculators

If you find this tool useful, explore the full Calculators collection or browse our complete tool directory. KX Toolkit is built for marketers, developers, designers, students and anyone who needs a quick utility without signing up for yet another SaaS.

What inputs does the triangle calculator accept?
You can solve any triangle from three known pieces, as long as at least one is a side. Common cases are SSS (three sides), SAS (two sides and the included angle), ASA (two angles and the included side), AAS (two angles and a non-included side), and SSA (two sides and a non-included angle). AAA (three angles only) does not pin down size, so it is rejected.
Which formulas does it use?
Law of cosines for SSS and SAS, law of sines for ASA, AAS, and SSA. Area is computed by Heron's formula when all three sides are known, or by half times two sides times the sine of the included angle otherwise. Perimeter is just the sum of the sides. The calculator picks the right formula automatically based on what you enter.
What is the ambiguous case in SSA?
When you give two sides and a non-included angle, there can be zero, one, or two valid triangles. If the side opposite the given angle is too short, no triangle exists. If it is exactly the right length, you get a right triangle. If it is between, you may get two distinct triangles (one acute, one obtuse). The calculator returns both solutions when applicable.
Why do my angles not add up to exactly 180 degrees?
Floating-point rounding. The calculator works to many decimal places internally, but displayed values are rounded for readability. If the displayed angles sum to 179.99 or 180.01, that is normal rounding error, not a calculation mistake. The internal values do sum to 180 to full precision; only the rounded display shows the discrepancy.
Where is triangle math used in practice?
Surveying and GPS triangulation, structural engineering, navigation, computer graphics (every 3D model is a mesh of triangles), and trigonometry-heavy fields like astronomy and aviation. Roof pitch calculations, ramp design, and even kitchen layouts depend on triangle relationships. Knowing how to solve any triangle from limited information is one of the most reused geometric skills.
How do I know whether my inputs form a valid triangle?
Three sides must satisfy the triangle inequality: the sum of any two sides must exceed the third. Three angles must sum to 180 degrees and each must be positive. Lengths and angles must all be positive numbers. The calculator checks these conditions and rejects impossible inputs with a clear message instead of producing nonsense.

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