StraightToolsArea Calculator
Calculate the area of common shapes.
Area formulas
Rectangle: length × width. Triangle: base × height ÷ 2. Circle: π × radius². Square: side².
When to use this tool
Use the area calculator for rectangles, triangles, circles, and squares. It is useful for rough flooring, paint, landscaping, fabric, and geometry estimates when dimensions use the same unit.
How the result is calculated
Rectangle area is length × width; triangle area is base × height ÷ 2; circle area is π × radius²; square area is side². The output is in square units corresponding to the dimensions you entered.
Worked example
A 10-by-12 rectangle has an area of 120 square units. A circle with radius 10 has an area of about 314.16 square units.
What to keep in mind
Make sure all dimensions use the same unit before calculating. Material purchases often require extra allowance for waste, cuts, overlap, or irregular shapes.
About our calculations
StraightTools is designed to show the method behind the answer, not just the result. Inputs are handled in your browser for this tool. For important financial, legal, medical, tax, safety, or contractual decisions, verify the result with an appropriate authoritative source or qualified professional.