Area Calculator
Area Calculator
Find area for 10 common 2D shapes or combine rectangles for rooms, floor plans, and cutouts.
Rectangle
96 m²
A = length × width
Perimeter
40 m
Uses the dimension unit
1,033.34
ft²
0.02
ac
9.60e-3
ha
Project estimate and precisionAllowance, unit cost, decimal places
Add a waste or overage allowance, then optionally multiply by a cost in the selected result unit.
Area is two-dimensional and is reported in square units. All dimensions for a shape use the same selected length unit.
Formula
Rectangle A=lw; square A=s^2; circle A=pi r^2; triangle A=bh/2; trapezoid A=(a+b)h/2; parallelogram A=bh; ellipse A=pi ab; sector A=(theta/360)pi r^2; annulus A=pi(R^2-r^2); regular polygon A=ns^2/[4tan(pi/n)] A_{circle}=\pi r^2 A_{triangle}=\frac{1}{2}bh A_{trapezoid}=\frac{a+b}{2}h A_{ellipse}=\pi ab A_{annulus}=\pi(R^2-r^2) - Choose one of 10 supported 2D shapes and enter the dimensions named for that formula.
- The calculator converts every length to a common base before converting the area to your selected square unit.
- Use composite mode to add rectangular regions and subtract rectangular cutouts.
- Perimeter appears only when the entered dimensions determine it without guessing missing sides.
Example
Worked example: rectangular room with a cutout
- 1 Add the main rectangle: 12 m x 8 m = 96 m².
- 2 Subtract the cutout: 3 m x 2 m = 6 m².
- 3 Composite area = 96 m² - 6 m² = 90 m².
- 4 With a 10% material allowance: 90 m² x 1.10 = 99 m².
The net floor area is 90 m², or 99 m² including the example allowance.
How
- Choose Single shape or Add / subtract areas.
- Select the shape, dimension unit, and desired square-unit result.
- Enter positive dimensions; angles use degrees and regular polygons require a whole number of sides.
- Review area, available perimeter, common unit equivalents, and the active diagram.
- Optionally add a project allowance and cost per selected square unit.
Avoid
- Entering a circle diameter in a field labeled radius.
- Using a slanted triangle or parallelogram side instead of the perpendicular height.
- Mixing measurement units instead of converting every dimension to the selected length unit.
- Treating area units as linear units; 1 m² is not 1 ft².
- Subtracting cutouts that overlap or exceed the added regions.
FAQ
Which shapes are supported?
Rectangle, square, circle, triangle, trapezoid, parallelogram, ellipse, circle sector, annulus, and regular polygon are supported.
Can I calculate an irregular room or floor plan?
Use Add / subtract areas to combine rectangular sections and remove rectangular cutouts. Divide more complex plans into non-overlapping rectangles first.
Why is perimeter not shown for every shape?
Base and height can determine area without determining every side. The calculator shows perimeter only when the entered dimensions are sufficient.
What happens when I change the dimension unit?
Existing dimensions are converted to preserve the same physical shape. If the result unit was paired with the old length unit, it follows the new square unit.
How does the project estimate work?
The allowance increases the calculated area by a percentage. Optional cost multiplies that adjusted area by the cost per selected square unit; no currency conversion is performed.
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