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Area Calculator

Find the area of a rectangle, square, triangle, circle, trapezoid, parallelogram or ellipse, in square units, square feet, square meters and acres.

Results

ItemValue

Steps

StepWorking
Enter all sizes in the same unit. Height is measured at a right angle to the base. Answers are rounded to 4 decimal places.

Quick Answer

Area is the flat space inside a shape, in square units. A rectangle is length × width, so a 20 ft by 12 ft room is 240 sq ft. A circle is π × r², so a radius of 6 ft gives about 113.10 sq ft. A triangle is base × height ÷ 2.

Last updated: 2 November 2026 · How we calculate this: standard area formulas

Table of Contents

How This Area Calculator Works

Pick a shape and a unit, then enter the sizes. The calculator shows the area in your unit and also in square feet, square meters and acres, with the formula and working.

Quick explanation: area = the space a flat shape covers, in square units such as ft².

  • Height: always measured at a right angle to the base.
  • Radius: half the diameter.
  • Rooms and floors: try our Square Footage Calculator.

Core Formulas

  • Rectangle: A = l × w
  • Square: A = s²
  • Triangle: A = b × h ÷ 2
  • Circle: A = π × r²
  • Trapezoid: A = (a + b) ÷ 2 × h
  • Parallelogram: A = b × h
  • Ellipse: A = π × a × b

Worked Example

A garden bed is a trapezoid. The parallel sides are 8 ft and 12 ft, and it is 5 ft deep.

  • A = (8 + 12) ÷ 2 × 5
  • A = 10 × 5 = 50 sq ft

Tips for Odd Shapes

  • L-shaped rooms: split them into rectangles and add the areas.
  • Cut-outs: subtract the area of any part you do not need.
  • Units: 1 sq yd = 9 sq ft, and 1 acre = 43,560 sq ft.

Frequently Asked Questions

Use the formula for the shape. For a rectangle, multiply length by width.

Multiply π by the radius squared. A circle with a radius of 3 has an area of about 28.27.

Multiply the base by the height, then divide by 2.

One acre is 43,560 square feet.

Area is the space inside a shape. Perimeter is the distance around it.

References & Sources

SourceUsed ForLink
Wikipedia, Area Area formulas for common shapes. https://en.wikipedia.org/wiki/Area
NIST, Unit conversion US customary and metric area units. https://www.nist.gov/pml/owm/metric-si/unit-conversion