Triangle — base and height
Area and perimeter, with the formula worked through and a drawing to scale.
Result
- Area
- 20 sq ft
- = 20 sq ft · 1.8581 m²
- Perimeter
- 20.8062 ft
- = 20.8062 ft · 6.3417 m
- Left side
- 6.4031 ft
- Right side
- 6.4031 ft
The working
Area: A = b × h ÷ 2
Perimeter: P = b + two slanted sides
A = b × h ÷ 2 = 8 × 5 ÷ 2 = 20 sides = √(x² + h²) and √((b − x)² + h²) = 6.4031 and 6.4031 P = 20.8062
Values in feet; areas in sq ft.
About the triangle — base and height
Any triangle is half of a parallelogram with the same base and height. Tell it where the peak sits along the base and it also works out the two slanted sides for the perimeter.
Every formula on this site is explained step by step in Learn: area and perimeter.
Other shapes
Square Rectangle Parallelogram Rhombus Trapezoid (trapezium) Kite Triangle — three sides Right triangle Isosceles triangle Equilateral triangle Triangle — two sides and the angle between Circle Semicircle Quarter circle Sector (pie slice) Circular segment (arch) Ring (annulus) Ellipse (oval) Regular polygon (pentagon, hexagon, octagon…) L-shape Any polygon — by corner points