Triangle Calculator

Calculate area, perimeter, angles, and sides of triangles using various methods and formulas

Triangle Results

Area
-
Square units
Perimeter
-
Linear units
Angle A
-
Degrees
Angle B
-
Degrees
Angle C
-
Degrees
Triangle Type
-
Classification

Triangle Results

Area
-
Square units
Perimeter
-
Linear units
Third Side
-
Linear units
Other Angles
-
Degrees

Triangle Results

Area
-
Square units
Perimeter
-
Linear units
Third Angle
-
Degrees
Other Sides
-
Linear units
💡 Enter any two values to calculate the third

Right Triangle Results

Area
-
Square units
Perimeter
-
Linear units
Side A
-
Linear units
Side B
-
Linear units
Hypotenuse
-
Linear units
Angles
90°, -, -
Degrees

How to Use the Triangle Calculator

Our comprehensive triangle calculator supports multiple calculation methods to solve any triangle problem:

📐 SSS (Side-Side-Side)

When you know all three sides of a triangle, use this method to find all angles and other properties. Uses Heron's formula for area calculation and the Law of Cosines for angles.

📏 SAS (Side-Angle-Side)

When you know two sides and the included angle between them. Perfect for problems where you have two sides meeting at a known angle. Calculates the third side using the Law of Cosines.

📊 ASA (Angle-Side-Angle)

When you know two angles and the side between them. Uses the Law of Sines to find the remaining sides. The third angle is automatically calculated since angles sum to 180°.

⟂ Right Triangle

Specialized calculator for right triangles (one 90° angle). Enter any two sides to find the third using the Pythagorean theorem. Automatically calculates angles using trigonometric functions.

🔢 Calculated Properties

• Area: Using appropriate formulas (Heron's, 0.5×base×height, 0.5×a×b×sin(C))
• Perimeter: Sum of all three sides
• All Angles: Using Law of Cosines and Law of Sines
• Triangle Type: Acute, obtuse, or right triangle classification
• Missing Sides: Calculated using appropriate geometric laws

💡 Pro Tips

• Ensure triangle inequality: sum of any two sides > third side
• All angles must sum to exactly 180 degrees
• Use decimal values for more precise calculations
• Right triangle mode automatically handles Pythagorean relationships
• Visual representation helps verify your calculations

Frequently Asked Questions

The triangle inequality states that the sum of any two sides of a triangle must be greater than the third side. For sides a, b, c: a+b>c, a+c>b, and b+c>a. If this rule isn't satisfied, the triangle cannot exist.
Use SSS when you know all three sides, SAS when you know two sides and the included angle, ASA when you know two angles and the side between them, and Right Triangle mode when you have a 90° angle and need to use Pythagorean theorem.
Right triangles have one 90° angle, acute triangles have all angles less than 90°, and obtuse triangles have one angle greater than 90°. Our calculator automatically determines and displays the triangle type.
Our calculator uses high-precision mathematical formulas including Heron's formula, Law of Cosines, and Law of Sines. Results are typically accurate to 6-8 decimal places, which is suitable for most practical applications.
Yes! Our calculator fully supports decimal inputs for both sides (in any units) and angles (in degrees). This allows for precise calculations in engineering, construction, and scientific applications.