The math behind your estimate
The inputs, allowance, and rounding stay visible.
- Rectangle
- Area = Length × Width
- Square
- Area = Side²
- Circle
- Area = π × (Diameter ÷ 2)²
- Triangle
- Area = ½ × Base × Height
- Total
- Total = sum of all added areas
Assumptions
- Areas are treated as flat planes. Sloped surfaces (like roofs) measure larger than their footprint — measure along the surface, or use a dedicated roof calculator.
- Triangle height means the perpendicular distance from the base to the opposite corner, not the length of a slanted side.
Frequently asked questions
- How do I measure the square footage of an irregular room?
- Split it into rectangles (and triangles if needed), measure each one, and add them together. An L-shaped room is just two rectangles — use the 'add another rectangle' button and name each section so you can check your work.
- How many square feet are in a 12×12 room?
- A 12 ft × 12 ft room is 144 square feet. For flooring or paint you'd typically add 5–10% on top for cuts and waste — the material calculators here handle that for you.
- How do I convert square feet to square meters?
- Divide square feet by 10.764. This calculator does it automatically — switch the unit toggle to m/cm and the total is shown in square meters.
- Can I mix feet and meters in one calculation?
- Yes. Each measurement field accepts inputs like 12' 6", 3.8m, or 96" and converts them internally, so you can measure with whatever tape you have on hand.
Sources
- Standard plane-geometry area formulas