How do I calculate the area of a circle?

The area of a circle is calculated using the formula A = π × r², where r is the radius of the circle. Simply enter the radius and our calculator will compute the area automatically.

Can I calculate area for irregular shapes?

Our calculator handles regular geometric shapes. For irregular shapes, you may need to break them down into simpler shapes or use approximation methods like the trapezoidal rule.

How accurate are the area calculations?

Our calculator uses precise mathematical formulas and provides accurate results. The accuracy depends on the precision of your input measurements and the mathematical constants used (like π).

Area Calculator

Choose a shape and enter every dimension in the same length unit. The area is that unit squared. For a circle, enter the radius, not the diameter.

Select Shape *

Length (m) *

Width (m) *

Smart Tips

• Always use consistent units when measuring - convert all dimensions to the same unit first

• For irregular shapes, break them down into basic shapes and add the areas together

• Square footage is essential for flooring, painting, and real estate calculations

• Remember that doubling the dimensions quadruples the area (area scales with the square)

• Use the same unit for all inputs (e.g. all in feet or all in meters) to avoid errors

• For circles, use radius (not diameter) in the formula unless the formula specifies diameter

Area Formulas

Shape	Formula
Rectangle	Area = Length × Width
Circle	Area = π × Radius²
Triangle	Area = ½ × Base × Height
Square	Area = Side²
Trapezoid	Area = ½ × (Base1 + Base2) × Height
Parallelogram	Area = Base × Height
Ellipse	Area = π × Semi-Major Axis × Semi-Minor Axis

Key Insights

Common Shapes

Calculate area for rectangles, circles, triangles, and other geometric shapes with precise formulas.

Unit Consistency

Always use consistent units (all in meters, all in feet, etc.) for accurate area calculations.

Real-World Applications

Area calculations are essential in construction, landscaping, interior design, and property measurement.

Precision Matters

For construction and design projects, precise area measurements are critical for material planning and cost estimation.

Frequently Asked Questions

The area of a circle is calculated using the formula A = π × r², where r is the radius of the circle (π is approximately 3.14159). The radius is the distance from the center to the edge—if you have the diameter, divide it by two to get the radius. Simply enter the radius and our calculator will compute the area automatically in your chosen units. Square the radius first, then multiply by π for the result.

Area measures the space inside a shape (in square units such as m² or ft²), while perimeter measures the distance around the shape (in linear units such as meters or feet). Area answers "how much surface is covered"—useful for flooring, paint, or land. Perimeter answers "how long is the boundary"—useful for fencing or trim. A shape can have the same perimeter but different areas, or the same area but different perimeters.

Our calculator handles regular geometric shapes (rectangle, circle, triangle, etc.). For irregular shapes, break the figure into parts that match those shapes—for example, an L-shaped room into two rectangles—then add the areas. For curves or complex boundaries, approximation methods like the trapezoidal rule or Simpson's rule can estimate area from a series of measurements. Surveyors and architects often use software that applies these methods to real-world plots.

Use consistent units for all measurements in a single calculation. Common units include square meters (m²), square feet (ft²), square inches (in²), and square centimeters (cm²). Metric conversions: 1 m² = 10,000 cm²; 1 ft² ≈ 0.093 m². For real estate or flooring, square feet or square meters are typical. Always use the same unit for length and width so the result is in the corresponding square unit—mixing feet and meters will give an incorrect result.

Our calculator uses standard mathematical formulas and provides results that are as accurate as your inputs. The formulas themselves are exact; accuracy depends on the precision of the measurements you enter (e.g., rounding radius or side lengths) and the value of π used in circle calculations. For practical uses like flooring or painting, rounding to two decimal places is usually sufficient.

The formulas in the table are the ones the page calculates. Circle and ellipse use the browser value of π. There is no conversion between square meters and square feet: the result is in square units of the lengths you type. Source: NIST SP 811: https://www.nist.gov/pml/special-publication-811.

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Area

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Note:Area calculations are based on standard geometric formulas. For real-world work, confirm measurements and consider irregularities in the surface or shape.