Area Calculator
Calculate the area of common 2D shapes — rectangles, triangles, circles, trapezoids, ellipses, sectors and more.
How to use the Area Calculator
- Enter your inputs into the Area Calculator above.
- Results update instantly as you type — no submit button needed.
- Adjust any value to see how the result changes in real time.
Common area formulas
Rectangle: l·w · · · Triangle: ½·b·h · · · Circle: π·r² · · · Trapezoid: ½(b₁+b₂)·h
Area measures 2D space and is expressed in square units (m², ft², in²). Convert units as needed: 1 m² = 10.76 ft²; 1 acre = 43,560 ft².
Worked example
A 12 ft × 8 ft rectangular room: 96 ft². A circular pool of radius 10 ft: π × 100 ≈ 314.2 ft². A trapezoidal piece of land with parallel sides 50 m and 80 m, height 30 m: ½(50+80)·30 = 1,950 m².
Frequently asked questions
How is area different from volume?
Area measures 2D surface (length × width). Volume measures 3D space (length × width × height). A 10 ft × 10 ft floor has 100 ft² of area; an 8 ft tall room with that floor has 800 ft³ of volume.
How do I find area of an irregular shape?
Break it into recognizable pieces (rectangles, triangles), find each area, and sum. For truly irregular shapes, planimeters or computer methods estimate area from a digitized outline.
Why is the area of a circle πr²?
Derived by integration — the area is the limit of approximating polygons inscribed in the circle. The constant π represents the ratio of circumference to diameter and shows up in all circle geometry.