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Triangle Calculator

Solve any triangle - find missing sides and angles

💡 Enter at least 3 values (sides and/or angles). The calculator will find the rest!

Sides

Angles (degrees)

Triangle Solution Methods

SSS (Side-Side-Side)

All three sides known → Use Law of Cosines to find angles

SAS (Side-Angle-Side)

Two sides and included angle → Use Law of Cosines for third side, then Law of Sines

ASA (Angle-Side-Angle)

Two angles and included side → Find third angle, then use Law of Sines

AAS (Angle-Angle-Side)

Two angles and non-included side → Find third angle, then use Law of Sines

SSA (Side-Side-Angle) - Ambiguous Case

Two sides and non-included angle → May have 0, 1, or 2 solutions

Triangle Types

By Sides

Equilateral: All sides equal (all angles 60°)
Isosceles: Two sides equal
Scalene: All sides different

By Angles

Acute: All angles less than 90°
Right: One angle exactly 90°
Obtuse: One angle greater than 90°

Important Formulas

Law of Sines

a/sin(A) = b/sin(B) = c/sin(C)

Law of Cosines

c² = a² + b² - 2ab·cos(C)

Heron's Formula (Area)

Area = √(s(s-a)(s-b)(s-c)), where s = (a+b+c)/2

Angle Sum

A + B + C = 180°

How to Use This Calculator

1

Enter Your Values

Input the required values in the calculator fields above. Make sure all inputs are valid numbers.

2

Click Calculate

Press the "Calculate" button to perform the calculation and see your results.

3

Review Results

Review the calculated results displayed below. Use these values for your needs.

About Triangle Calculator

The Triangle Calculator is a useful tool for calculating triangle values. This calculator helps you quickly and accurately determine the results you need for your calculations.

When to Use This Calculator

  • Quick Calculations: Get instant results without manual computation
  • Accuracy: Ensure precise calculations every time
  • Planning: Use for project planning and estimation
  • Verification: Double-check your manual calculations

Why Use Our Calculator?

  • ✅ Instant Results: Get accurate calculations immediately
  • ✅ Easy to Use: Simple interface for all skill levels
  • ✅ 100% Free: No registration or payment required
  • ✅ Mobile Friendly: Works on all devices
  • ✅ Accurate: Precise mathematical calculations

Tips for Best Results

  • Double-Check Inputs: Verify all values before calculating
  • Use Valid Numbers: Ensure inputs are valid numbers
  • Review Results: Check results for reasonableness
  • Clear and Retry: Clear inputs if you need to recalculate
Frequently Asked Questions

Can any three numbers be sides of a triangle?

No. The triangle inequality states that the sum of any two sides must be greater than the third side. For example, 1, 2, and 5 cannot form a triangle.

What if I only know two sides?

You need at least one angle as well. Two sides alone have infinite solutions - they could form triangles with different angles.

Why is SSA ambiguous?

With two sides and a non-included angle, you might be able to form two different triangles, one triangle, or no triangle at all. This is called the ambiguous case.

What's the difference between ASA and AAS?

ASA: the known side is between the two known angles. AAS: the known side is not between the two known angles. Both solve the same way.

Can a triangle have more than one obtuse angle?

No. Since all angles must sum to 180°, having two angles greater than 90° would exceed 180°, which is impossible.