Add and subtract up to twenty rectangular, circular, triangular, trapezoidal or ring-shaped areas, with square feet, square yards and square meters.
How to use this tool
- Choose a shape for each area and enter its dimensions and unit.
- Use Add for included regions and Subtract for deliberate deductions. Avoid unintended overlap.
- Add up to twenty areas; a quantity repeats one identical area. An optional price applies per net square foot.
- Select Calculate and check every signed area contribution before using the net total.
Formula and unit basis
Rectangle = length × width; circle = πr²; triangle = base × perpendicular height ÷ 2; trapezoid = (parallel side A + parallel side B) × perpendicular height ÷ 2; ring = π(outer radius² − inner radius²). Add signed area contributions after converting units.
Worked examples
A 20 ft × 15 ft bounding rectangle minus an 8 ft × 5 ft missing corner gives 260 ft². For a 12 ft × 10 ft rectangle with a 4 ft base by 3 ft perpendicular-height triangle removed, the result is 114 ft².
Assumptions and interpretation
Areas must not overlap unless a deliberate subtraction corrects the overlap. Triangle/trapezoid height is perpendicular, not a sloping edge. This is geometric area for project planning; it does not certify an appraisal, legal listing area, floor layout, waste allowance or building-code measurement standard.
Project guides
- Measure an Irregular Floor: L-Shapes, Alcoves and Cutouts
- From Net Floor Area to Flooring Cartons: Coverage, Allowance and Rounding
Choose the related tool for the next question
Explore Construction calculators or return to the GreenCalc home page for other subjects.
Frequently asked questions
How do I subtract a missing corner?
Add the bounding shape and add a second area marked Subtract for the missing corner.
Can I combine different measurement units?
Yes. Each area has its own unit selector, and the signed areas are converted before summing.
Does the result certify a home listing area?
No. It is a geometric project-area calculator and does not certify an appraisal or other measurement standard.