Calculate area for common 2D shapes. Choose a shape, enter the needed measurements, and get the formula, result, and steps.
Rectangle area
- Choose the correct shape.
- Enter the measurements required by the formula.
- Substitute the values and calculate the square-unit result.
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All calculations run locally in your browser. Your entered values are not sent to an external service.
How do I use the area calculator?
Use the area calculator by selecting a shape, entering the required measurements, and selecting Calculate Area. The result shows the area in square units and lists the formula steps.
What does area mean?
Area is the amount of flat surface inside a two-dimensional shape. Area uses square units because it counts unit squares that cover the shape.
Length is one-dimensional. Area is two-dimensional. Volume is three-dimensional.
What area formulas are included?
This calculator includes rectangles, squares, triangles, circles, parallelograms, trapezoids, ellipses, and circle sectors.
Each formula matches a shape attribute. Rectangles use length and width. Circles use radius. Trapezoids use two bases and height.
What are area calculation examples?
Rectangle example
A rectangle with length 8 and width 5 has area 8 × 5 = 40 square units.
Triangle example
A triangle with base 10 and height 6 has area (10 × 6) / 2 = 30 square units.
Circle example
A circle with radius 7 has area π × 7² ≈ 153.94 square units.
What is the area formula chart?
| Shape | Formula | Required values |
|---|---|---|
| Rectangle | A = l × w | length, width |
| Square | A = s² | side |
| Triangle | A = bh / 2 | base, height |
| Circle | A = πr² | radius |
| Trapezoid | A = (a + b)h / 2 | two bases, height |
| Ellipse | A = πab | semi-major and semi-minor axes |
What area mistakes should I avoid?
Using diameter instead of radius
Circle area uses radius. Divide diameter by 2 before using A = πr².
Forgetting square units
Area is measured in square units, such as cm², m², ft², or units².
Using slant height as triangle height
Triangle area uses perpendicular height, not side length unless that side is perpendicular to the base.
Mixing measurement units
Convert all measurements to the same unit before calculating area.
Area Calculator FAQs
How do you calculate rectangle area?
Multiply length by width. A rectangle with length 8 and width 5 has area 40 square units.
How do you calculate triangle area?
Multiply base by height, then divide by 2. The formula is A = bh / 2.
How do you calculate circle area?
Square the radius and multiply by π. The formula is A = πr².
Why is area written in square units?
Area counts two-dimensional surface coverage. The unit is squared because the measurement combines two lengths.
Are my values sent to a server?
No. The calculation runs locally in your browser.
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Reviewer
This non-medical math content is reviewed under the SolverCalc reviewer rule by Prof. Dr. Khalil Mudassar. WordPress adds the author bio automatically, so this page does not include a duplicate author box.
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Sources
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Disclaimer
This calculator is for educational and practical geometry use. For construction, engineering, or legal measurements, verify dimensions and formulas with the required professional standard.