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
Choose how numeric results are displayed. The selected decimal separator (dot or comma) will also be used when parsing input numbers.
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.