Square Footage Calculator
Area of one room or many, in feet and inches or metric, with optional waste.
Areas
= 168" (14')
= 138" (11' 6")
= 108" (9')
= 42" (3' 6")
Results update as you typeLive
Square Footage · Result
CalculatedAREA
192.5 square feet
- Net area
- 192.5 ft²
- Waste
- 0%
- Areas
- 2
- Largest
- 161.00 ft²
Output unit defaulted to ft² because at least one length was entered in imperial units
SUGGESTED DEFAULTCode references & assumptions · 1
How this result is supported
- SUGGESTED DEFAULTOutput unit defaulted to ft² because at least one length was entered in imperial units
- ASSUMPTION
What do these evidence labels mean?
- PRIMARY-VERIFIED
- directly supported by one authoritative primary source, quoted with section/page/figure
- CROSS-VERIFIED
- independently supported by two or more appropriate authoritative sources
- DERIVED
- mathematically derived from PRIMARY-VERIFIED values; the derivation is preserved in data and in code
- INTERPRETED
- a source exists but translating it into calculator behaviour required interpretation
- CONVENTION
- recognised trade practice, not a mandatory provision
- ASSUMPTION
- product/design assumption or useful default with no authoritative basis
- UNVERIFIED
- insufficient authoritative evidence
Code references and product data are quoted in the units their source uses.
Reference checks are informational, not compliance determinations.
How square footage is calculated
Each area is length × width, and entries are summed. A count on an entry multiplies it, so four identical rooms are one line rather than four, and the line still shows what one of them is.
Waste is applied once, after the sum, because that is how material is bought. Applying it per room and adding the results gives the same number here, but stops being true the moment rounding to a purchase unit enters — which is why the calculator keeps net and gross separate and names the percentage it used.
Feet-and-inch input is parsed as a fraction, not as a decimal approximation, so 12′ 7⁵⁄₈″ is exact until the moment it is displayed.
A = length × width
Area of one rectangle.
net = Σ (A × count)
Every entry added up, each with its own quantity.
gross = net × (1 + waste)
Waste is applied once, to the total — not per room.