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Square footage calculator
Floor or footprint area from length and width in feet. Same inputs, same answer, every time — this is the exact math Ask Donnie's estimator runs on.
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How it’s computed
Area = length (ft) × width (ft), quantized to 0.01 sqft with decimal (never floating-point) arithmetic.
Decimal-exact and deterministic: identical inputs always return identical results. This is the same math Ask Donnie’s estimating engine runs — not an approximation, and never a language model doing arithmetic.
Common questions
How do I measure an L-shaped or irregular room?
Split it into rectangles, run each through the calculator, and add the results. Every straight-walled plan decomposes into rectangles.
Is this floor area or wall area?
Floor/footprint area. For walls, use the wall area calculator — it takes perimeter × height and subtracts door and window openings.
Related calculators
Need the whole estimate, not just this number?
Ask Donnie turns a description or a plan into a full itemized estimate — deterministic math, real cited pricing, an AACE accuracy class. Free to start, watermarked deliverables included.