What formulas are used?

The tool uses the Law of Cosines for side-angle calculations, Heron's formula for area from three sides, and standard trigonometric identities.

Can it detect if a triangle is valid?

Yes. It checks the triangle inequality theorem (sum of any two sides must exceed the third) and shows an error for invalid inputs.

What properties does it calculate?

All three sides, all three angles, area, perimeter, inradius (inscribed circle), circumradius (circumscribed circle), and triangle type classification.

Does it work with decimal values?

Yes. You can enter decimal (non-integer) side lengths and angles for precise calculations.

Triangle Calculator

Calculate triangle sides, angles, area, perimeter, and more. Supports SSS, SAS, and special triangles.

triangle calculatortriangle areapythagoreantriangle solver

Disclaimer: This tool provides estimates for informational and educational purposes only. It does not constitute professional financial, medical, or legal advice. Please consult with a qualified professional before making any significant decisions based on these estimations.

Common Use Cases

double-checking day-to-day calculations
sanity-checking numbers before sharing them
fast answers on mobile without a spreadsheet

What is Triangle Calculator?

The Triangle Calculator is a comprehensive geometry tool that solves triangles given different sets of known values. Enter three sides (SSS) to find all angles and properties, or two sides and the included angle (SAS) to compute the missing side. It also includes special triangle modes for right, equilateral, and isosceles triangles. The tool calculates area, perimeter, inradius, circumradius, and classifies the triangle type (scalene/isosceles/equilateral and acute/right/obtuse).

How to Use This Tool

1Choose input mode: three sides (SSS), two sides and angle (SAS), or special triangle
2Enter the known values
3See all computed properties: missing sides, angles, area, perimeter, and radii

Example

Input

Sides: 3, 4, 5

Output

Right triangle, Area: 6, Angles: 36.87, 53.13, 90

Before You Rely on This Result

UtilityNest keeps tools in this category focused on transparency: short instructions, a worked example, and plain-language guidance so you can review the result before you depend on it.

Check that the inputs reflect your real situation before you rely on the estimate.
Rules, rates, health needs, and legal requirements may vary by country, state, insurer, or provider.
Use this result as a starting point, then confirm important decisions with official sources or a qualified professional.

Frequently Asked Questions

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