Select a 2D shape, enter its dimensions, and get the exact area — in any unit you need. Supports 8 shapes with step-by-step formulas and metric/imperial conversion.
8 shapes supported Metric & imperial Step-by-step formula Unit conversion SVG diagram per shape
Area Calculator — Find the Area of Any 2D Shape
This free area calculator computes the exact area of eight common 2D shapes: rectangle, square, triangle, circle, ellipse, trapezoid, parallelogram, and circular sector. Just select a shape, enter the required dimensions, choose your unit, and press Calculate. The result appears instantly along with the formula used, a worked example, and the area expressed in multiple unit conversions.
Whether you're a student solving geometry homework, a contractor estimating flooring or paint coverage, a designer planning a layout, or just curious about a shape — this tool gives you the right answer with zero guesswork.
Area Formulas for Every Shape
Each shape uses a specific area formula. Here's the complete reference:
RectangleA = width × height
SquareA = side²
TriangleA = ½ × base × height
CircleA = π × r²
EllipseA = π × a × b
TrapezoidA = ½ × (a+b) × h
ParallelogramA = base × height
SectorA = ½ × r² × θ
Example — Circle: Radius = 7 m → A = π × 7² = π × 49 ≈ 153.94 m² Example — Rectangle: Width = 12 ft, Height = 5 ft → A = 12 × 5 = 60 ft² Example — Triangle: Base = 10 cm, Height = 6 cm → A = ½ × 10 × 6 = 30 cm²
How to Use the Area Calculator
Select your shape from the dropdown. The input fields and diagram update automatically for the chosen shape.
Enter the dimensions — width and height for rectangles, radius for circles, base and height for triangles, and so on.
Choose your unit — millimeters, centimeters, meters, kilometers, inches, feet, yards, or miles.
Click "Calculate Area" — the result displays instantly with the area in your chosen unit plus conversions to other common units.
For the triangle, you can switch between the base/height method and Heron's formula (using all three side lengths) — useful when you don't know the perpendicular height.
Real-World Uses for Area Calculation
Home ImprovementCalculate floor area for tiles, carpet, or hardwood; wall area for paint; or roof area for shingles. Avoid over- or under-buying materials.
School & GeometryVerify homework answers, practice area formulas, or understand the geometry behind each shape with step-by-step formula breakdowns.
Gardening & LandMeasure lawn, garden bed, or plot area for fertiliser, seed, or irrigation planning. Works in metric and imperial for any country.
Engineering & DesignCompute cross-sectional areas of components, material sheet sizes, or space planning for architectural and product design work.
Crafts & FabricEstimate fabric, paper, or material needed for sewing, quilting, wrapping, or any craft project using circular or polygonal shapes.
Solar & EnergyCalculate roof or panel area for solar installation planning, or compute window area for heat loss and insulation estimates.
Area Unit Conversion Reference
Area units scale by the square of the linear unit factor — so 1 meter = 100 cm but 1 m² = 10,000 cm². This trips up many people doing manual conversions. Our calculator handles it automatically, but here's a quick reference:
From
To
Multiply by
1 m²
cm²
10,000
1 m²
mm²
1,000,000
1 km²
m²
1,000,000
1 ft²
in²
144
1 yd²
ft²
9
1 mi²
yd²
3,097,600
1 m²
ft²
10.764
1 ft²
m²
0.0929
The calculator results also show automatic cross-unit display — so if you calculate in meters, you also see the result in cm², ft², and in² without any extra steps.
Frequently Asked Questions
The calculator supports eight shapes: rectangle, square, triangle, circle, ellipse, trapezoid, parallelogram, and circular sector. Each shape has dedicated input fields that update dynamically, plus a visual diagram and the formula being used.
Select "Triangle" and then switch the triangle type to "All Three Sides (Heron's Formula)". Enter the three side lengths a, b, and c — the calculator uses Heron's formula: s = (a+b+c)/2, then Area = √(s × (s−a) × (s−b) × (s−c)). This is accurate for any triangle where you know all three sides but not the perpendicular height.
Both have the same area formula (base × height), but "height" means different things. For a rectangle, height equals the side length because all angles are 90°. For a parallelogram, height is the perpendicular distance between the two parallel sides — not the slant side length. Make sure to enter the perpendicular height, not the slant height.
A sector is a "pie slice" of a circle. Its area is: A = ½ × r² × θ, where r is the radius and θ is the central angle in radians. If you enter the angle in degrees, the calculator converts it automatically (degrees × π/180 = radians). A full circle (360°) gives A = π × r², which is the standard circle area formula.
Yes. Select any unit from the dropdown — millimeters, centimeters, meters, kilometers, inches, feet, yards, or miles — and the result automatically shows the area in your selected unit plus several convenient conversions. Remember that area conversions involve squared factors, so 1 m = 100 cm but 1 m² = 10,000 cm².
The area of an ellipse is A = π × a × b, where a is the semi-major axis (half the longest diameter) and b is the semi-minor axis (half the shortest diameter). For a circle where a = b = r, this simplifies to the familiar A = π × r².
The calculator re-runs the area formula using dimensions in the chosen unit. If you entered 5 meters and switch to centimeters, it treats your input as 5 centimeters — a much smaller dimension. To get the same physical area in different units, use the unit conversion table in the results or the Area Converter tool.
Yes. All formulas use full floating-point precision with JavaScript's built-in Math.PI and Math.sqrt functions. Results are accurate to at least 6 significant figures. For construction or engineering, always verify critical measurements with certified tools, but this calculator is suitable for estimation, planning, and checking manual calculations.
People Also Search For
Related geometry and measurement tools on CalcPocket:
