These are the terms you’ll meet when measuring area and ordering materials. Each links to the calculator or guide where it’s used.
Area & measurement basics
- Square Footage
- The area of a two-dimensional surface expressed in square feet — the total number of one-foot-by-one-foot squares that fit inside a boundary.
- Area
- The size of a two-dimensional surface, measured in square units such as square feet, square yards or square meters.
- Perimeter
- The total distance around the outside edge of a shape. Unlike area, it is a length, measured in feet.
- Linear Feet
- A measurement of length in a single straight line, as opposed to area (square feet) or volume (cubic feet).
- Square Yard
- A unit of area equal to 9 square feet. Divide square feet by 9 to get square yards.
- Acre
- A unit of land area equal to 43,560 square feet. Divide square feet by 43,560 to get acres. Calculator →
- Cubic Yard
- A unit of volume equal to 27 cubic feet, used to order bulk materials like concrete, mulch and gravel. Calculator →
- Waste Factor
- An extra percentage of material added to the calculated area to cover cuts, breakage and mistakes — typically 5–15%.
Geometry terms
- Radius
- The distance from the center of a circle to its edge; exactly half the diameter.
- Diameter
- The distance straight across a circle through its center; exactly twice the radius.
- Circumference
- The distance around the edge of a circle, equal to π × diameter.
- Pi (π)
- The mathematical constant (about 3.14159) that relates a circle's circumference and area to its radius and diameter.
- Apothem
- The perpendicular distance from the center of a regular polygon to the midpoint of any side.
- Annulus
- A ring-shaped region between two concentric circles. Its area is π × (R² − r²). Calculator →
- Sector
- A pie-slice portion of a circle bounded by two radii and an arc. Its area is a fraction of the full circle. Calculator →
- Circular Segment
- The region of a circle between a chord and its arc — the sector minus the triangle.
- Semicircle
- Exactly half of a circle, divided along its diameter. Its area is ½ × π × radius². Calculator →
- Ellipse
- An oval defined by a semi-major axis (a) and semi-minor axis (b). Its area is π × a × b. Calculator →
- Trapezoid
- A four-sided shape with one pair of parallel sides. Its area is ½ × (a + b) × height. Calculator →
- Parallelogram
- A four-sided shape with two pairs of parallel sides. Its area is base × perpendicular height. Calculator →
- Rhombus
- A parallelogram with four equal sides. Its area is ½ × diagonal₁ × diagonal₂. Calculator →
- Heron's Formula
- A method to find a triangle's area from its three side lengths, without needing the height. Calculator →
- Shoelace Formula
- A method to compute a polygon's exact area from the coordinates of its corners; used in land surveying. Calculator →
- Regular Polygon
- A polygon with all sides and all angles equal, such as a regular hexagon, octagon or decagon.
Real estate & construction
- Gross Living Area (GLA)
- The finished, above-grade living space of a home measured under the ANSI Z765 standard. It excludes garages, unfinished areas and basements. Calculator →
- ANSI Z765
- The U.S. national standard, 'Square Footage – Method for Calculating,' used to measure single-family residential square footage. Required by Fannie Mae for appraisals. Calculator →
- Roofing Square
- A unit of roof area equal to 100 square feet. Roofing materials and labor are priced by the square. Calculator →
- Pitch Multiplier
- A factor that converts a roof's flat footprint area to its true sloped area, based on the roof's pitch (rise over run). Calculator →