Rectangle & Square
A = l × w
Multiply the length by the width. For a square, multiply the side length by itself.
Geometry / Measurement
Area Calculator
Calculate the area of 12 common shapes. Choose a figure, enter your dimensions, and get the result with its formula and unit conversions—right here on the page.
Step 1
Select a shape
Choose the figure you want to measure
Step 2
Calculation method
Choose what you already know
Step 3
Measurement unit
Values convert when the unit changes
Step 4
Dimensions
Net area equals gross area minus this value. Boundary measurements remain unchanged.
Reset restores this shape’s sample values and Feet (ft).
How to Use the Area Calculator
Three quick steps turn the dimensions of a shape into an area measurement.
1
Select a shape
Choose rectangle, circle, triangle, or another figure in the calculator above.
2
Enter the dimensions
Provide the required lengths. Pick the measurement unit used for every length.
3
Read the result
See square units, the corresponding formula, and conversions to common area units.
Area Formulas for Common Shapes
Area measures the two-dimensional space inside a boundary. These formulas assume valid geometric shapes and measurements in consistent units.
Triangle
A = ½bh
Multiply the base by the perpendicular height, then divide by two.
Circle
A = πr²
Square the radius, then multiply by π. A diameter is twice the radius.
Trapezoid
A = (a + b)h / 2
Average the two parallel bases and multiply by the perpendicular height.
Parallelogram
A = bh
Use base times perpendicular height, not the slanted side length.
Ellipse
A = πab
Multiply the semi-major and semi-minor axes and π.
The interactive calculator also supports rhombuses, circular sectors, semicircles, annuli, and regular polygons. See the area formula guides for worked examples.
What Is Area and How Is It Calculated?
Area describes how much flat space a shape covers. Its unit is squared: 12 feet multiplied by 10 feet gives 120 square feet (ft²), not 120 feet.
Area vs. Perimeter
Area measures the surface enclosed by a shape. Perimeter measures the distance around its boundary. A rectangle measuring 12 ft by 10 ft has an area of 120 ft² and a perimeter of 44 ft. Both quantities are useful, but they answer different questions.
For triangles and parallelograms, the formula uses the perpendicular height. For circles, use the radius (half the diameter). For irregular outlines, divide the region into known shapes or use a polygon measurement method rather than assuming it is a rectangle.
Read the area vs. perimeter guide →Area Unit Conversion
The calculator automatically converts your result into square meters, square feet, acres, and hectares. These reference conversions use international standard units.
| Area unit | Equivalent in m² | Common use |
|---|---|---|
| 1 square foot (ft²) | 0.09290304 m² | Rooms, flooring |
| 1 square yard (yd²) | 0.83612736 m² | Carpet, landscaping |
| 1 acre | 4,046.8564224 m² | Land |
| 1 hectare | 10,000 m² | Large land areas |
A length conversion factor must be squared when converting area. For example, 1 ft = 0.3048 m, so 1 ft² = 0.3048² m².
Real-World Area Calculation Examples
Common area calculations appear in geometry homework, home improvement, landscaping, and property planning.
Room square footage
A rectangular room 12 ft long and 10 ft wide covers 120 ft². Measure each side at floor level before estimating flooring materials.
Circular garden bed
A round garden with a 3 m radius covers π × 3² = 28.27 m² (rounded to two decimals).
Rectangular parcel
A 100 ft × 200 ft parcel covers 20,000 ft², or about 0.459 acres. Legal acreage requires a reliable boundary survey.
Common Area Calculation Mistakes
Using diameter as radius
For circles, divide diameter by two before applying πr². Using the full diameter makes the result four times too large.
Mixing units
Convert lengths to a common unit first. Do not multiply 5 feet by 36 inches as though both numbers represented feet.
Using sloped height
Triangle and parallelogram formulas require the height at a right angle to the base—not an inclined edge.
Area Guides & Tutorials
Explore step-by-step instructions for specific shapes, measurements, and everyday examples.
How to Calculate the Area of a Circle
Use radius or diameter and understand why πr² works.
How to Find the Area of a Triangle
Learn base and height, with a worked example.
How to Calculate the Area of Irregular Shapes
Split compound figures into rectangles, circles, and triangles.
How to Calculate the Square Footage of a Room
Measure standard and L-shaped spaces.
Area vs. Perimeter
See the difference between surface and boundary length.
Square Feet to Square Meters
Convert area units without confusing them with length units.
Frequently Asked Questions
How do I calculate area?
Select the shape, measure its required dimensions, and apply its area formula. For a rectangle, multiply length by width. The calculator above handles these steps automatically.
What is the formula for area?
There is no single formula for every shape. A rectangle uses length × width, a triangle uses base × perpendicular height ÷ 2, and a circle uses π × radius².
How do I calculate square footage?
Measure lengths in feet. For a rectangular floor, multiply length in feet by width in feet to get square feet (ft²).
Can I calculate irregular land area here?
You can calculate simple component shapes and add their areas. Complex or curved property boundaries require a dedicated survey or geospatial measurement method.
What is the difference between area and perimeter?
Area is the space inside a shape in square units; perimeter is the length of its boundary in linear units.
Does this calculator support acres?
Yes. Results include an estimated conversion to acres and hectares. Exact survey measurements may require additional methods.