About this calculator
Use Heron’s formula calculator if you know all three sides.
How to use it
- Choose what you know.
- Enter the values.
- Read the area.
The formula
Area = ½ × base × height = ½ab sin C = ½ |x₁(y₂ − y₃) + x₂(y₃ − y₁) + x₃(y₁ − y₂)|
- C
- angle between sides a and b
Worked example
Three ways
- Base 10, height 6: area 30.
- Sides 8 and 11 with 40° between: area ≈ 28.28.
- Corners (0, 0), (6, 0), (2, 5): area 15.
What the result means
If three corners give area 0, they lie on one straight line.
Assumptions
- All lengths in the same unit.
Limitations
- Results are rounded to 10 significant figures.
Frequently asked questions
What is the area of a triangle?
Half of base × height.
How do I find area without height?
Use two sides and the angle, or Heron’s formula with three sides.
How do I find area from coordinates?
Use the coordinate (shoelace) formula.
Last reviewed on 3 October 2026. Found a mistake? Tell us.