Base area and the extra coverage allowance
Base area sums each entered rectangle, circle or triangle multiplied by its quantity. One allowance applies after all sections are totaled. Coverage is shown in both square feet and square metres, and material cost uses area including the allowance.
For flooring, the Tile Calculator converts surface area into tile and box quantities using tile dimensions and waste allowance.
For walls, the Paint Calculator accounts for openings, coats, and the product’s coverage rate.
The formula
One foot is exactly 0.3048 metre, so one square foot is 0.09290304 square metre. The allowance applies once after all entered sections are totaled. Circle area uses the numerical value of π.
Two 12 ft by 10 ft rooms
Each room is 120 ft², so two rooms total 240 ft². A 10% allowance adds 24 ft² for a planning total of 264 ft².
How to use this calculator
- Choose a single shape or several different sections. Enter rectangle length and width, circle diameter, or triangle base and perpendicular height.
- Set the quantity of equal shapes, or use Add section for a room list. Changing units converts dimensions and the price per area.
- Enter the extra allowance and optional material price under Advanced options. Review measured sections, total coverage and area cost.
Build a list of non-overlapping shapes
Add a row for each non-overlapping room or section. Choose rectangles, circles or triangles and repeat only shapes with identical dimensions.
For a triangle, the second measurement is its perpendicular height, not a sloped side. A circle uses a diameter; its second measurement is ignored. Keep different sections from overlapping so the total does not double-count shared area.
Choose allowance for the material
Cutting loss and breakage differ by product, layout, and room shape. The editable percentage is a planning input rather than a universal rule.
For products sold by boxes or containers, use the dedicated tile or paint calculator to include package rounding.
Assumptions & limitations
What this calculation assumes
- Entered sections do not overlap; each quantity repeats that row’s dimensions.
- Triangle height is perpendicular to the base, and circle entry uses diameter.
- One allowance and material price apply to the entire area total.
What to keep in mind
- No cutout subtraction, supplier package rounding or placement of individual material pieces.
- Measurements, geometry and the chosen allowance determine the planning estimate.
Common questions
How do I calculate several different rooms?
Choose Several different rooms or sections and add one row per room. Each row has its own shape, dimensions and quantity; the allowance is applied after summing the rows.
Why is the conversion factor squared?
Area has two dimensions, so both length and width must be converted.
Should I always add 10%?
No. Choose an allowance based on the material, layout, cuts, and supplier guidance.
Sources & further reading
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