Triangle Area Calculator
Quickly find the area of any triangle. Choose Base + height, Side + angle + side, Angle + side + angle, or Side + side + side. It’s free, shows instant results, and is friendly to local number formats (commas or dots).
Number Format
Select the number format you are comfortable with.
Triangle Area: Four Fast Ways
This calculator finds the area of a triangle using four different sets of known values. You can enter whole numbers or decimals. Angles must always be in degrees, and results are given in square units.
Base + height
The most straightforward method: if you know a side as the base and its perpendicular height.
Formula: Area = ½ × base × height
Example
Base = 8, Height = 5 → Area = 0.5 × 8 × 5 = 20 square units.
Side + angle + side (SAS)
Use when you know two sides and the angle between them.
Formula: Area = ½ × side₁ × side₂ × sin(included angle)
Example
Side₁ = 7, Side₂ = 9, Included angle = 40° → Area ≈ 20.25 square units.
Angle + side + angle (ASA)
Use when you know a side and the two angles at its ends.
Formula: Area = (side² × sin(angle₁) × sin(angle₂)) ÷ (2 × sin(angle₁ + angle₂))
Example
Side = 10, Angle₁ = 35°, Angle₂ = 65° → Area ≈ 26.45 square units.
Side + side + side (SSS)
Use when all three sides are known (Heron's formula).
Formula: Area = √(s(s − a)(s − b)(s − c)), where s = (a+b+c)/2.
Example
Sides = 6, 7, 8 → s = 10.5 → Area ≈ 20.34 square units.
Quick reference
| Given | Inputs | Area |
|---|---|---|
| Base + height | 8, 5 | 20 |
| SAS | 7, 9, 40° | 20.25 |
| ASA | 10, 35°, 65° | 26.45 |
| SSS | 6, 7, 8 | 20.34 |
FAQ
Do I need to enter units?
No. Just enter numbers. The result is in square units automatically.
Can I enter angles in radians?
No. Enter angles in degrees only.
Can I enter numbers in scientific notation?
No. Use plain numbers such as 12.5 instead of 1.25e1.
Which method should I use?
Choose the method that matches the values you already know: base and height, two sides and the angle between them, two angles and the included side, or all three sides.