Free Toolkit

Area CalculatorCalculate area and perimeter for 8 shapes — rectangle, circle, triangle, trapezoid, and more.

Area Calculator illustration
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Area Calculator

Calculate area and perimeter for 8 shapes — rectangle, circle, triangle, trapezoid, and more.

How to Use
1

Select Shape

Choose from 8 geometric shapes.

2

Enter Dimensions

Input the required measurements for your chosen shape.

3

View Results

See the calculated area, perimeter (where applicable), and formula.

What Is Area Calculator?

The Area Calculator computes the area (and perimeter where applicable) of eight common geometric shapes: rectangle, circle, triangle, trapezoid, ellipse, parallelogram, rhombus, and circular sector. Select a shape, choose your preferred unit of measurement, and enter the required dimensions. The calculator displays the area in square units, the perimeter in linear units, and the formula used. Multiple unit options are available including mm, cm, m, km, inches, feet, yards, and miles.

Why Use Our Area Calculator?

  • Eight shapes: rectangle, circle, triangle, trapezoid, ellipse, parallelogram, rhombus, sector
  • Shows both area and perimeter where applicable
  • Multiple unit options (metric and imperial)
  • Displays the formula used for each shape

Common Use Cases

Real Estate

Calculate floor areas, lot sizes, and room dimensions.

Construction

Determine material quantities from area calculations.

Education

Solve geometry problems and verify manual calculations.

Landscaping

Calculate garden beds, lawn areas, and planting zones.

Technical Guide

Area formulas by shape: Rectangle: A = l × w, P = 2(l+w). Circle: A = πr², P = 2πr. Triangle: A = ½bh. Trapezoid: A = ½(a+b)h. Ellipse: A = πab. Parallelogram: A = bh. Rhombus: A = ½d₁d₂. Circular Sector: A = ½r²θ (θ in radians). For the sector calculator, the angle input is in degrees and converted internally: θ_rad = θ_deg × π/180. Perimeter is computed where a simple formula exists. All area results are in square units of the selected unit; perimeter in linear units.

Tips & Best Practices

  • 1
    For irregular shapes, try breaking them into combinations of these basic shapes
  • 2
    Area in square units: if inputs are in meters, output is in square meters (m²)
  • 3
    A circle has the maximum area for a given perimeter among all 2D shapes
  • 4
    For triangles, you need base AND height — the height must be perpendicular to the base

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Frequently Asked Questions

QHow do I calculate the area of an irregular shape?
Break it into basic shapes (rectangles, triangles), calculate each area separately, and add them together. This is called the decomposition method.
QWhat is the difference between area and perimeter?
Area measures the surface enclosed by the shape (in square units). Perimeter measures the total length of the boundary (in linear units).
QWhat is the area of a triangle if I know all three sides?
Use Heron's formula: A = √(s(s-a)(s-b)(s-c)) where s = (a+b+c)/2. This calculator uses the base × height formula.
QHow do I find the radius from circumference?
r = Circumference / (2π). Then area = πr².
QWhat units should I use?
Use any consistent unit. The area will be in the square of that unit (e.g., meters → square meters). Don't mix units in the same calculation.

About Area Calculator

Area Calculator is a free online tool from FreeToolkit.ai. All processing happens directly in your browser — your data never leaves your device. No registration required. No ads. Just fast, reliable tools.