Area of a Triangle Calculator
The area of a triangle is ½ × base × height; with three sides, Heron's formula gives it directly: a triangle with sides 5, 6 and 7 cm has an area of 14.6969 cm².
Perpendicular height from the base to the opposite corner.
30 cm²
- Area
- 30 cm²
In other units: 0.003 m² · 3000 mm² · 3 × 10⁻⁹ km² · 3 × 10⁻⁷ ha · 0.0322917 ft² · 4.65001 in² · 0.00358797 yd² · 7.41316 × 10⁻⁷ ac · 1.15831 × 10⁻⁹ mi²
Step-by-step solution
- A = ½ × b × h
- A = ½ × 10 × 6 = 30 cm²
Area of a Triangle Formula
A = ½ b h = √[s(s−a)(s−b)(s−c)]
b base, h height, a b c sides, s = (a+b+c)/2
Worked Example
A triangle with sides 5, 6 and 7 cm:
- s = (a + b + c) ÷ 2 = (5 + 6 + 7) ÷ 2 = 9
- A = √[s(s − a)(s − b)(s − c)]
- A = √[9 × 4 × 3 × 2] = 14.6969 cm²
Perimeter: 18 cm
Same area in other units: 0.00146969 m² · 1469.69 mm² · 1.46969 × 10⁻⁹ km² · 1.46969 × 10⁻⁷ ha · 0.0158197 ft²
Frequently asked questions
How do I find the area of a triangle with 3 sides?
Use Heron's formula: s = (a + b + c) ÷ 2, then A = √[s(s − a)(s − b)(s − c)]. For sides 3, 4 and 5, s = 6 and A = √(6 × 3 × 2 × 1) = 6.
What is the area of an equilateral triangle?
A = (√3 ÷ 4) a², about 0.433 a². An equilateral triangle with 10 cm sides has an area of 43.30 cm².
What is the area of a right triangle?
Half the product of the two legs: A = ½ × a × b, because one leg is the height of the other. Legs of 3 and 4 give 6.
How do I use the formula with two sides and an angle?
A = ½ × a × b × sin C, where C is the angle between sides a and b. Sides 5 and 6 with a 60° angle give about 12.99.
Sources
- The International System of Units (SI), 9th edition (SI Brochure), Bureau International des Poids et Mesures .
- Guide for the Use of the International System of Units (SI), NIST Special Publication 811, 2008 Edition, National Institute of Standards and Technology .
Last reviewed: . Factors are stored exactly and computed with 50-digit decimal arithmetic. See how we verify conversion factors.
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APA
Scientific Converters. (2026, October 15). Area of a Triangle Calculator. Retrieved October 25, 2026, from https://scientificconverters.com/calculators/area-of-a-triangle/
IEEE
Scientific Converters, "Area of a Triangle Calculator," scientificconverters.com. Accessed: Oct. 25, 2026. [Online]. Available: https://scientificconverters.com/calculators/area-of-a-triangle/