Area Calculator
Calculate the area and perimeter of rectangles, triangles, circles, trapezoids, ellipses, sectors and regular polygons, converted to m², ft² and acres.
Find the area of the common flat shapes — rectangles, squares, triangles, circles, ellipses, trapezoids, parallelograms, rhombuses, circle sectors and regular polygons — in any length unit. Along with the area you get the perimeter where the measurements allow it, the formula with your numbers filled in, and the area converted to square meters, square feet, acres and hectares for flooring, paint, garden or land jobs.
How to use this tool
- Pick the shape; the list shows what a, b and c stand for.
- Enter the measurements, all in the same unit, and choose that unit.
- Read the area and perimeter, and check the formula line.
- Use the table to see the same area in other units.
Formula
Rectangle A = l × w · Triangle A = ½ × b × h · Circle A = πr²
Trapezoid A = ½(a + b)h · Heron A = √(s(s − a)(s − b)(s − c)), s = (a + b + c) ÷ 2
Regular polygon A = n s² ÷ (4 tan(180° ÷ n)) · Sector A = (θ ÷ 360) πr²
The area comes out in the unit you chose, squared. The height of a triangle, parallelogram or trapezoid is the perpendicular distance between base and top, not the slanted side. The ellipse perimeter uses Ramanujan’s approximation, which is within 0.5% even for very flat ellipses and far closer for typical ones.
Example
A room measuring 5 m by 4 m has an area of 5 × 4 = 20 m² and a perimeter of 18 m; the table shows that is about 215.28 ft². A round patio with a 3 m radius covers π × 3² ≈ 28.27 m².
Frequently asked questions
How do I find the area of an L-shaped room?
Split it into rectangles, find each area here and add them. A 6 m × 4 m room with a 2 m × 2 m corner missing is 24 − 4 = 20 m².
How do I convert square feet to square meters?
Multiply by 0.09290304. One foot is exactly 0.3048 m, and 0.3048² = 0.09290304. The conversion table does this for you.
Can I find a triangle’s area without its height?
Yes. If you know all three sides, choose "Triangle from 3 sides" and Heron’s formula is used; a 3–4–5 triangle has an area of 6.
Does the rhombus option work for a kite?
For the area, yes: any four-sided shape whose diagonals cross at right angles, including a kite, has area d₁ × d₂ ÷ 2. The perimeter shown applies to a rhombus only.
Last updated: 2026-10-30