Area Calculator

This area calculator finds the total two-dimensional space occupied by a flat shape or surface. Enter the known dimensions of your target shape, select your preferred measurement units, and click calculate. The calculator instantly applies the correct geometric formula and gives you the exact surface area in square units such as square feet, square meters, or acres.

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Enter measurements for the selected shape to calculate its area.

Portrait of Jose Smith

Created by Jose Smith

Last updated: September 28, 2026

How to Use the Area Calculator

Calculating surface space takes only a few seconds when you follow these simple steps.

  1. Select your geometric shape from the dropdown menu, such as a rectangle, circle, triangle, or trapezoid.
  2. Select your preferred input unit of measurement from options like inches, feet, yards, meters, centimeters, or kilometers.
  3. Input the required dimensions into the fields, such as length, width, radius, height, or base.
  4. Click the Calculate button to view the total surface area instantly.
  5. Convert your final answer into different square units using the unit conversion selector if needed.

Area Formulas for Common Geometric Shapes

Every flat figure relies on a specific mathematical equation to measure its interior surface. Here are the clear formulas used to solve the most common shapes.

Square Area Formula

A square is a four-sided figure where all sides have equal length. To calculate its area, multiply the side length by itself.

Area=a2\text{Area} = a^2

Variable: a = length of any side

Rectangle Area Formula

A rectangle features four right angles with opposite sides of equal length. Multiply the total length by the width to find its space.

Area=length×width\text{Area} = \text{length} \times \text{width}

Triangle Area Formulas

Triangle calculations depend on the measurements you have available.

Base and Height: Area=0.5×base×height\text{Base and Height: Area} = 0.5 \times \text{base} \times \text{height}
Three Sides (Heron’s Formula): Area=0.25×(a+b+c)(−a+b+c)(a−b+c)(a+b−c)\text{Three Sides (Heron's Formula): Area} = 0.25 \times \sqrt{(a+b+c)(-a+b+c)(a-b+c)(a+b-c)}
Two Sides and Included Angle: Area=0.5×a×b×sin⁡(γ)\text{Two Sides and Included Angle: Area} = 0.5 \times a \times b \times \sin(\gamma)

When working with three-sided shapes, our specialized triangle calculator helps solve unknown angle measurements alongside the surface space.

Circle Area Formula

A circle is a round shape where every outer edge point sits at an equal distance from the central point. The distance from the center to the edge is the radius.

Area=π×r2\text{Area} = \pi \times r^2

Variable: r = radius of the circle, π\pi (Pi) ≈ 3.14159

Circle Sector Area Formula

A sector represents a pie-slice section of a circle enclosed by two radii and an arc.

Area=(θ360)×π×r2\text{Area} = \left(\frac{\theta}{360}\right) \times \pi \times r^2

Variables: r = radius, θ\theta = central angle in degrees

Ellipse Area Formula

An ellipse resembles a squished circle or an oval. It uses two distinct radii named the semi-major axis and semi-minor axis.

Area=π×a×b\text{Area} = \pi \times a \times b

Variables: a = semi-major axis, b = semi-minor axis

Trapezoid Area Formula

A trapezoid is a four-sided figure with at least one pair of parallel sides called bases.

Area=(a+b2)×height\text{Area} = \left(\frac{a+b}{2}\right) \times \text{height}

Variables: a = top base, b = bottom base

Parallelogram Area Formula

A parallelogram features two pairs of parallel opposite sides.

Base and Height: Area=base×height\text{Base and Height: Area} = \text{base} \times \text{height}
Sides and Angle: Area=a×b×sin⁡(θ)\text{Sides and Angle: Area} = a \times b \times \sin(\theta)

Rhombus Area Formula

A rhombus has four equal sides with slanted angles.

Diagonals Method: Area=d1×d22\text{Diagonals Method: Area} = \frac{d_1 \times d_2}{2}
Base and Height Method: Area=base×height\text{Base and Height Method: Area} = \text{base} \times \text{height}

Kite Area Formula

A kite has two pairs of equal-length adjacent sides.

Area=d1×d22\text{Area} = \frac{d_1 \times d_2}{2}

Variables: d1 and d2 = lengths of the two intersecting diagonals

Regular Polygon Area Formulas

Regular polygons feature equal side lengths and equal interior angles.

Pentagon: Area=0.25×25+105×a2\text{Pentagon: Area} = 0.25 \times \sqrt{25 + 10\sqrt{5}} \times a^2
Hexagon: Area=(3×32)×a2\text{Hexagon: Area} = \left(\frac{3 \times \sqrt{3}}{2}\right) \times a^2
Octagon: Area=2×(1+2)×a2\text{Octagon: Area} = 2 \times (1 + \sqrt{2}) \times a^2
General Regular Polygon: Area=n×a24×tan⁡(180∘/n)\text{General Regular Polygon: Area} = \frac{n \times a^2}{4 \times \tan(180^\circ / n)}

Variables: a = side length, n = total number of sides

How to Calculate the Area of Irregular Shapes

Irregular shapes do not follow a single simple geometric equation. However, you can calculate their surface space by breaking them down using a simple process called polygon triangulation or decomposition.

  1. Split the complex figure into smaller, standard shapes like triangles, rectangles, and semicircles.
  2. Measure the essential dimensions for each individual subshape.
  3. Apply the individual geometric formula to each smaller section.
  4. Add all the resulting numbers together to get the grand total surface space.

If your project involves multi-dimensional structures rather than flat surfaces, explore our surface area calculator to evaluate 3D objects like cylinders, cones, and prisms.

Real-World Applications of Area Calculations

Knowing how to calculate flat surface space is vital across many practical everyday scenarios.

  • Home Improvement: Estimating the exact amount of flooring, tile, carpet, or paint required for a room renovation saves money and prevents material waste.
  • Land Measurement: Real estate agents and land surveyors measure property plots, yards, and agricultural fields in square feet or acres.
  • Construction and Roofing: Builders calculate the area of roofs, concrete slabs, and walls to determine structural requirements and cost estimates.
  • Gardening and Lawn Care: Gardeners evaluate total lawn area to apply the correct amount of grass seed, fertilizer, and topsoil.

Frequently Asked Questions

What is area in simple terms?

Area is the total amount of two-dimensional space that a flat object or shape covers. It is measured in square units.

What geometric shape provides the largest area for a fixed perimeter?

A circle provides the absolute largest surface space among all two-dimensional shapes with the same perimeter length.

What quadrilateral yields the largest space for a set perimeter?

A square always yields the largest interior surface space among all four-sided quadrilaterals with a given perimeter.

What is the difference between area and perimeter?

Perimeter measures the total boundary distance around the outside edge of a shape. Area measures the actual surface space enclosed inside those boundaries.

How do I convert square feet to square meters?

Divide your total square feet measurement by 10.764 to convert it directly into square meters.

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