Area Calculator

Calculate the area and perimeter of common shapes — rectangle, circle, triangle, trapezoid, and ellipse.

Inputs

Shape

Length

Width

Radius

Base

Height (Triangle)

Tab to move between fields

Results

Area

300 sq ft

≈ 7 king-size beds

Perimeter70 ft

Area (metric)27.87 m²

Area (acres)0.0069 acres

How to Use This Calculator

Select the shape from the dropdown (rectangle, circle, triangle, trapezoid, or ellipse).
Enter the required dimensions that appear for your chosen shape (e.g., length and width for a rectangle).
Area formulas used: rectangle = l × w; circle = πr²; triangle = ½ × base × height; trapezoid = ½(a+b)×h; ellipse = πab.
Perimeter or circumference is also computed alongside area for each shape.
All dimension inputs must be positive; units are not converted — ensure all dimensions use the same unit.
For irregular polygons or composite shapes, break the shape into known sub-shapes and sum their areas.

How the result changes with Length

Length	Area
10,000	150,000 sq ft
35,000	525,000 sq ft
65,000	975,000 sq ft
90,000	1,350,000 sq ft

What each input means

Shape: The geometric shape to calculate.
Length: Length of the shape or side.
Width: Width of the shape or side.
Radius: Distance from center to edge.
Base: Base length of the shape.

How this is calculated

Worked example, using the default values

Identify Input Parameters
4 parameters
Shape = 0, Length = 20, Width = 15, Radius = 10 = 11 input(s) provided
Calculate Area
Area
300 = 300
Calculate Perimeter
Perimeter
70 = 70
Calculate Area
Area
27.87 = 27.87

Engine last updated July 11, 2026. Checked against 2 independently-derived tests — how we verify calculators.

The questions that sit next to this one — chosen by subject, including calculators filed under a different category.

Construction & Building Trades

Square Footage Calculator

Calculate the square footage of a rectangular area. Convert between square feet, yards, and meters. Estimate total cost based on price per square foot.

Geometry & Measurement