Area Calculator

What is area?

Area is the size of a flat surface, measured in square units such as square feet, square metres or acres. Knowing an area helps when buying flooring, paint, carpet, turf, fabric or land.

Area formulas

Rectangle: length × width. Triangle: ½ × base × height, or Heron's formula √(s(s − a)(s − b)(s − c)) from three sides with s = half the perimeter. Trapezoid: (b₁ + b₂)/2 × h. Circle: πr². Sector: πr² × angle/360°. Ellipse: πab. Parallelogram: base × height.

Worked example: a room 30 ft by 20 ft has an area of 600 sq ft, which is 55.74 m². A triangle with sides 30, 45 and 50 ft has s = 62.5 and area √(62.5 × 32.5 × 17.5 × 12.5) ≈ 666.9 sq ft.

Irregular shapes

Split an irregular area into rectangles, triangles and circles, find each area and add them. For curved outlines, measure offsets at regular intervals and use the trapezoid rule.

Unit conversions

1 square foot = 0.0929 m². 1 square yard = 9 sq ft. 1 acre = 43,560 sq ft ≈ 4,046.86 m². 1 hectare = 10,000 m² ≈ 2.471 acres.

Frequently asked questions

How do I find area from perimeter? You cannot without knowing the shape.

Why are units squared? Area counts squares of the unit length.

How much extra flooring should I buy? Usually 5–10% for cuts and waste.