Square Inch Calculator
Square Inch Calculator works out Area and Area including waste from Shape, Length / diameter / base and Width / triangle height / second parallel side. The default figures on this page give area (square inches) of 864 in2; 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 = 3 ft x 2 ft = 6 ft^2
- Reported in square inches: 6 ft^2 = 864 in2
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 Inch 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 Inch Calculator
Enter Shape, Length / diameter / base, Width / triangle height / second parallel side and Distance between the parallel sides. 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, Length / diameter / base, Width / triangle height / second parallel side, Distance between the parallel sides, Additional areas to add and Waste / cutting allowance.
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
Is a square inch 4 inches?
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 and width / triangle height / second parallel side 10 — the area (square inches) is 864 in2. Put your own figures in their place and the working updates beside the result.
Is a square inch the same as an inch?
It needs Shape, Length / diameter / base, Width / triangle height / second parallel side, Distance between the parallel sides, Additional areas to add and Waste / cutting allowance. Nothing else is required, and the figures stay in your browser.
How many square inches is 12x12 inches?
On the figures this page opens with — length / diameter / base 12 and width / triangle height / second parallel side 10 — the area (square inches) is 864 in2. 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 information do I need for the Square Inch Calculator?
You need Shape, Length / diameter / base, Width / triangle height / second parallel side, Distance between the parallel sides, Additional areas to add, Waste / cutting allowance, Length unit and Coverage per box / gallon / roll. The page opens with default figures that give area (square inches) of 864 in2, so you can see the scale before entering your own.
What does this Square Inch 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 Inch 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.