Area Calculator
Rectangles, circles, triangles and trapezoids — added up, with waste.
Shape
= 168" (14')
= 138" (11' 6")
Results update as you typeLive
Area · Result
CalculatedAREA
161 square feet
- Net area
- 161 ft²
- Waste
- 0%
- Shape
- Rectangle
- Output unit
- 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 area is calculated
A real room is rarely one rectangle. Each shape is entered separately, converted to a common unit, and summed — so a room with a bay window is a rectangle plus a trapezoid rather than an estimate.
Circles are entered by diameter because that is the measurement a tape gives you across a floor; the radius is derived rather than asked for. The trapezoid takes its two parallel sides and the perpendicular distance between them, which is the height, not the sloping edge.
Waste is applied once to the total and reported as its own figure, so the net area stays visible next to the number you would buy against.
rectangle: A = length × width
circle: A = π × diameter² ÷ 4
By diameter, not radius — it is what a tape measures.
triangle: A = ½ × base × height
trapezoid: A = ½ × (a + b) × height
a and b are the two parallel sides.