Square Foot Estimate Calculator
Square foot estimate calculator works out Area and Area including waste from Shape, Report the area in and Length / diameter / base. The default figures on this page give estimated cost of 1,275.00; change any entry and the result, the working and the sources update together.
Your figures
Updates as you typeHow this is worked out
2 steps
- Plan area = 20 ft x 15 ft = 300 ft^2
- Estimated cost = 1275
Its 8 worked examples are re-run on every release, last on 15 September 2026. What changed
Sources and references
3 sources
Keep this result
Save it, change one figure, then compare the two
The calculation stays free. Save this scenario, adjust one assumption, save that too, and put them side by side to see exactly what the change costs you. A free account keeps 5 scenarios and 2 comparisons; Personal makes both unlimited and adds exports and private links. Nothing is saved unless you press Save.
What the square foot estimate calculator calculates
Calculates floor or wall area for rectangular, square, round, triangular, trapezoidal or elliptical spaces, adds a waste allowance and estimates material quantity and cost.
How to use this square foot estimate calculator
Enter Shape, Report the area in, Length / diameter / base and Width / triangle height / second parallel side. Area updates as you type. Change one figure at a time to see what drives the result.
How the result is worked out
Open “How this is worked out” beside the result for the step-by-step calculation behind Area, Area including waste and Area (square feet).
The method follows NIST Special Publication 811, Guide for the Use of the International System of Units (exact 1 ft = 0.3048 m, 1 acre = 43,560 ft2), Weisstein, Eric W. "Trapezoid", "Ellipse" and "Circle". MathWorld — A Wolfram Web Resource and Ramanujan, S. "Modular Equations and Approximations to pi" (1914) — second approximation used for the ellipse perimeter.
What you can compare
Change one input at a time to see how it affects Area, Area including waste and Area (square feet). The inputs you can vary are Shape, Report the area in, Length / diameter / base, Width / triangle height / second parallel side, Distance between the parallel sides and Additional areas to add.
Results are general information, not financial, tax, legal, medical or engineering advice. Check any decision that matters with a qualified professional.
See something wrong? Report a problem with this calculator
Frequently asked questions
How do I estimate square feet?
Calculates floor or wall area for rectangular, square, round, triangular, trapezoidal or elliptical spaces, adds a waste allowance and estimates material quantity and cost. Open “How this is worked out” beside the result to see each step for your own figures.
Can I estimate square footage using Google Maps?
Calculates floor or wall area for rectangular, square, round, triangular, trapezoidal or elliptical spaces, adds a waste allowance and estimates material quantity and cost. On the figures this page opens with — length / diameter / base 12, width / triangle height / second parallel side 10 and waste / cutting allowance 10% — the estimated cost is 1,275. Put your own figures in their place and the working updates beside the result.
What is a 12x12 room in square feet?
Calculates floor or wall area for rectangular, square, round, triangular, trapezoidal or elliptical spaces, adds a waste allowance and estimates material quantity and cost. On this page it is computed from Shape, Report the area in and Length / diameter / base and shown as Area, Area including waste and Area (square feet).
What information do I need for the square foot estimate calculator?
You need Shape, Report the area in, Length / diameter / base, Width / triangle height / second parallel side, Distance between the parallel sides, Additional areas to add, Waste / cutting allowance and Length unit. The page opens with default figures that give estimated cost of 1,275.00, so you can see the scale before entering your own.
What does this square foot estimate calculator show?
It shows Area, Area including waste, Area (square feet), Area (square metres), Area (square yards), Area (square inches), Area (acres) and Area (hectares), with the working and any warnings for your entries.
Can I check how the square foot estimate calculator result was calculated?
Yes. The “How this is worked out” section shows the calculation steps, and the sources section identifies the references used for the method.