Instantly calculate the area and perimeter of a square, rectangle, circle, triangle and parallelogram. Pick the shape and enter the dimensions.
Enter the dimensions
Pick the shape and enter the dimensions. Results compute instantly.
Standard geometry formulas. Instant in-browser calculation, no account. Exact results for the dimensions you enter.
Each 2D shape has its own formulas for area (the inner surface) and perimeter (the outline length). Pick the shape and enter the dimensions:
A circle with radius 5: area = π × 25 ≈ 78.54, circumference ≈ 31.42. A 3-4-5 triangle: area = 6, perimeter = 12.
Square area = side × side (side²). Perimeter = 4 × side. For side 5: area = 25, perimeter = 20.
Rectangle area = length × width. Perimeter = 2 × (length + width). For 4 × 3: area = 12, perimeter = 14.
Circle area = π × radius². Circumference (perimeter) = 2 × π × radius. For radius 5: area ≈ 78.54, circumference ≈ 31.42.
With Heron’s formula from the three sides: s = (a+b+c)/2, area = √(s(s−a)(s−b)(s−c)). For 3, 4, 5: area = 6. Alternatively, area = base × height ÷ 2.
Parallelogram area = base × height. Perimeter = 2 × (side a + side b). For base 4 and height 3: area = 12.
Area is the surface inside the shape (in square units, m²), while the perimeter is the length of the outline (in linear units, m).
Perimeter in length units (cm, m, km) and area in the matching square units (cm², m², km²).
A formula that gives a triangle’s area from its three side lengths without knowing the height: area = √(s(s−a)(s−b)(s−c)), where s is the semi-perimeter.
Take the square root of the area. If area = 49, side = √49 = 7.