Math Calculators
Area Calculator
Calculate area for rectangles, squares, triangles, circles, trapezoids, parallelograms, and ellipses with formulas and square units.
Enter the values and review the result.
Use the same unit for every dimension.
Calculation assumptions
- *Dimensions can be zero or positive numbers.
- *Use the same unit for every dimension in one calculation.
- *Circle calculations use radius, not diameter.
- *Area results are shown in square units such as square feet or square meters.
- *Project estimates may need waste allowance, material coverage rates, and professional measurements.
Enter all dimensions required for the selected shape to calculate area.
Results and breakdowns will appear here after a valid calculation.
What the Area Calculator does
Area measures the flat surface inside a two-dimensional shape. Use this calculator for rectangles, squares, triangles, circles, trapezoids, parallelograms, and ellipses.
It is useful for school geometry, square footage checks, wall area, flooring, paint, patios, concrete forms, garden beds, fabric, and other material planning.
When you switch shapes, the calculator shows only the dimensions used by the new formula and recalculates the result for that shape. All dimensions must use the selected unit.
Area formula table
| Shape | Inputs needed | Formula |
|---|---|---|
| Rectangle | Length, width | Area = length x width |
| Square | Side | Area = side^2 |
| Triangle | Base, height | Area = base x height / 2 |
| Circle | Radius | Area = pi x radius^2 |
| Trapezoid | Base 1, base 2, height | Area = (base 1 + base 2) x height / 2 |
| Parallelogram | Base, height | Area = base x height |
| Ellipse | Radius a, radius b | Area = pi x a x b |
Worked area examples
Rectangle room area
A room that is 12 ft by 10 ft uses Area = 12 x 10 = 120 square feet.
Circle area
A circular patio with a 5 ft radius uses Area = pi x 5^2 = about 78.54 square feet.
Triangle area
A triangular section with a 10 ft base and 6 ft height uses Area = 10 x 6 / 2 = 30 square feet.
Project planning example
For flooring, paint, concrete, gravel, or mulch, start with area, then check coverage, depth, waste, and product labels before buying material.
Area vs perimeter
Area measures the surface inside a shape. Perimeter measures the distance around the outside edge.
For example, a room floor needs area for flooring, but trim around the room often needs perimeter. If you later need depth, use the Volume Calculator.
Common area units
Area is measured in square units because two dimensions are multiplied together. Common units include square inches, square feet, square yards, square centimeters, and square meters.
Keep every input in the same unit. If you have mixed units, convert first with the Unit Converter or Length Converter.
Common mistakes
- Mixing different units, such as feet for length and inches for width.
- Using diameter instead of radius for a circle.
- Confusing area and perimeter.
- Forgetting that area uses square units.
- Rounding too early before the final result.
This calculator provides general area estimates. Real projects may need waste allowance, material coverage rates, shape adjustments, or professional measurements.
Related project calculators
For project planning, try the Square Footage Calculator, Paint Calculator, Concrete Calculator, Gravel Calculator, Mulch Calculator, Construction Calculators, or Math Calculators.
Transparency note
Accuracy and limitations
Calzivo tools are built for practical estimates, conversions, and checks. Some tools use standard formulas or simplified assumptions, and results can be affected by input accuracy, rounding, units, local rules, or changing official requirements.
Results depend on the values you enter and any simplified assumptions used by the tool. Verify important results before making decisions or submitting official information.
Reference check
Sources and references
These references provide background context for the topic. They do not replace official advice or documents for personal decisions.
- Geometric Formulas
OpenStax, Prealgebra 2e
- Properties of Rectangles, Triangles, and Trapezoids
OpenStax, Prealgebra 2e
- Area of an Ellipse
Harvey Mudd College Mathematics
How to Use This Tool
Use these steps to enter the right inputs and interpret the result correctly.
Select the shape you want to calculate the area for.
Choose the measurement unit and enter the required dimensions.
The result updates when you change the shape or dimensions. Review the area, formula, substitution, and plain-English explanation.
Related Tools
Use these tools when area turns into square footage, volume, materials, or unit conversions.
Square Footage Calculator
Calculate room and surface area, subtract wall openings, add waste, and optionally apply a user-entered USD-per-square-foot price.
Volume Calculator
Calculate volume for cubes, boxes, cylinders, spheres, cones, pyramids, and prisms with cubic unit conversions.
Unit Converter
Convert common length, mass, and temperature units.
Length Converter
Convert between 11 length units with standards-based factors.
Paint Calculator
Calculate paintable area with opening deductions, user-entered whole coats, product-label coverage, and optional container cost planning.
Concrete Calculator
Calculate multi-shape concrete volume with user-entered overage, optional product-label bag yield, and optional ready-mix or bag cost.
Gravel Calculator
Calculate gravel volume with optional supplier-density US-short-ton, product-label bag, overage, and user-entered cost estimates.
Mulch Calculator
Calculate mulch volume with optional product-label bag, overage, and user-entered cost estimates without a universal depth preset.
Related Guides
Background reading and explanations related to Area Calculator.
Frequently Asked Questions
Common questions about Area Calculator and how to read the result.
How do I calculate area?
Choose the shape, enter the required dimensions in the same unit, and apply that shape formula. For example, rectangle area is length times width.
What is the formula for rectangle area?
Rectangle area = length x width. A 12 ft by 10 ft rectangle has an area of 120 square feet.
What is the formula for circle area?
Circle area = pi x radius^2. Use radius, not diameter. If you have diameter, divide it by 2 first.
What is the difference between area and perimeter?
Area measures the surface inside a shape. Perimeter measures the distance around the outside of a shape.
Why is area measured in square units?
Area multiplies two dimensions, such as feet times feet, so the result is square feet, square meters, or another square unit.
Can I use this for square footage?
Yes. Choose feet as the unit and the result is square feet. For room-focused workflows, use the Square Footage Calculator.
Can I calculate area with different units?
Convert dimensions to the same unit before calculating. Mixing inches and feet in the same formula can create incorrect results.
Does this include material waste?
No. The area result does not include waste, cuts, overlap, coverage rates, or extra material. Add those separately for real projects.