Square Feet Room Calculator
Room Square Footage Calculator works out Area and Area including waste from Length / diameter / base, Width / triangle height / second parallel side and Distance between the parallel sides. The default figures on this page give area (square feet) of 120 ft2; 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 = 12 ft x 10 ft = 120 ft^2
- Reported in square feet: 120 ft^2 = 120 ft2
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 Room Square Footage 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 Room Square Footage Calculator
Enter Length / diameter / base, Width / triangle height / second parallel side, Distance between the parallel sides and Additional areas to add. 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 Length / diameter / base, Width / triangle height / second parallel side, Distance between the parallel sides, Additional areas to add, Waste / cutting allowance and Length unit.
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 many sq ft is in a 12x12 room?
On the figures this page opens with — length / diameter / base 12 and width / triangle height / second parallel side 10 — the area (square feet) is 120 ft2. No single number fits everyone: change any figure above and the answer updates as you type, with each step of the arithmetic beside it.
What size is a 300 sq ft room?
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 Length / diameter / base, Width / triangle height / second parallel side and Distance between the parallel sides and shown as Area, Area including waste and Area (square feet).
What is the formula for calculating square feet?
It needs Length / diameter / base, Width / triangle height / second parallel side, Distance between the parallel sides, Additional areas to add, Waste / cutting allowance and Length unit. Nothing else is required, and the figures stay in your browser.
How many sq is a 10x10 room?
The result gives Area, Area including waste, Area (square feet), Area (square metres), Area (square yards) and Area (square inches), each labelled with its unit so the figure can be read on its own.
What information do I need for the Room Square Footage Calculator?
You need Length / diameter / base, Width / triangle height / second parallel side, Distance between the parallel sides, Additional areas to add, Waste / cutting allowance, Length unit, Coverage per box / gallon / roll and Price per unit area. The page opens with default figures that give area (square feet) of 120 ft2, so you can see the scale before entering your own.
What does this Room Square Footage 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.