Area Calculator
Calculate area for any shape — rectangles, triangles, circles, trapezoids, and irregular spaces. Get square footage for rooms, yards, and construction projects with unit conversion.
Enter your values above to see the results.
Tips & Notes
- ✓For L-shaped rooms, measure the full bounding rectangle first, then subtract the missing corner rectangle — this is faster and less error-prone than measuring each section of the L independently.
- ✓Always measure at multiple points along each wall for rooms and spaces — walls are rarely perfectly parallel, and averaging two measurements gives a more accurate area than assuming rectangular perfection.
- ✓For circular or irregular outdoor areas, break the shape into a grid and count the number of full grid squares plus estimate partial squares — this grid method produces accurate results for any shape without complex math.
- ✓Convert all measurements to the same unit before calculating — mixing feet and inches produces incorrect results. Either convert everything to decimal feet (6 inches = 0.5 feet) or everything to inches before multiplying.
- ✓Add 10% to any material order based on area calculations — measured areas are always optimistic, real spaces always have irregularities, and the cost of the buffer is small compared to the cost of a shortage.
Common Mistakes
- ✗Using the perimeter instead of the area — perimeter measures the boundary length (linear feet), while area measures the enclosed space (square feet). These are completely different quantities with different applications.
- ✗Forgetting to convert inches to feet before multiplying for rectangular areas — a room measured as 144 inches × 168 inches is 24,192 square inches = 168 square feet, not 24,192 square feet.
- ✗Applying the rectangle formula to triangular areas without dividing by 2 — a triangle with base 15 ft and height 8 ft has area 60 sq ft, not 120 sq ft.
- ✗Ignoring slope when calculating roofing or hillside areas — the actual surface area of a sloped surface is always greater than its horizontal footprint projection, often by 10–40% depending on pitch.
- ✗Measuring indoor rooms to the center of walls rather than to the finished wall surface — this introduces error, especially in rooms with thick walls or multiple layers of trim.
Area Calculator Overview
Area is the measure of two-dimensional space enclosed within a boundary — the foundational calculation that underlies every material quantity estimate in construction, landscaping, and real estate. Whether you are calculating flooring, sod, paint coverage, or land value, every downstream quantity depends on the accuracy of the initial area measurement. Knowing which formula to apply to which shape, and how to decompose complex shapes into simpler ones, is the practical skill this calculator supports.
Rectangle and square area:
Area = Length × Width
EX: Room 14.5 ft × 11 ft = 159.5 sq ft | Square patio 12 ft × 12 ft = 144 sq ftTriangle area — three methods depending on available measurements:
Area = ½ × Base × Height (when base and perpendicular height are known)
EX: Triangular garden bed, base 15 ft, height 8 ft → Area = ½ × 15 × 8 = 60 sq ftCircle and partial circles:
Circle: Area = π × r² | Semicircle: Area = π × r² ÷ 2 | Sector: Area = π × r² × (angle ÷ 360)Area formulas for common construction shapes:
| Shape | Formula | Variables | Example |
|---|---|---|---|
| Rectangle | L × W | Length, Width | 20 × 12 = 240 sq ft |
| Triangle | ½ × b × h | Base, Height | ½ × 15 × 8 = 60 sq ft |
| Circle | π × r² | Radius | π × 5² = 78.54 sq ft |
| Trapezoid | ½ × (a+b) × h | Two parallel sides, Height | ½ × (10+14) × 6 = 72 sq ft |
| Parallelogram | b × h | Base, Height | 12 × 9 = 108 sq ft |
| Ellipse | π × a × b | Semi-major, Semi-minor axes | π × 8 × 5 = 125.66 sq ft |
| Regular hexagon | 3√3/2 × s² | Side length s | 3√3/2 × 6² = 93.53 sq ft |
| Unit | Square Feet | Square Yards | Square Meters | Acres |
|---|---|---|---|---|
| 1 square foot | 1 | 0.111 | 0.0929 | 0.0000230 |
| 1 square yard | 9 | 1 | 0.836 | 0.000207 |
| 1 square meter | 10.764 | 1.196 | 1 | 0.000247 |
| 1 acre | 43,560 | 4,840 | 4,047 | 1 |
| 1 hectare | 107,639 | 11,960 | 10,000 | 2.471 |
Frequently Asked Questions
Divide the shape into recognizable sub-shapes (rectangles, triangles, circles). Measure each sub-shape separately, calculate its area using the appropriate formula, and sum all the sub-areas. For outdoor areas with curved edges: superimpose a grid (graph paper or imaginary), count full squares, estimate partial squares as half-squares, and multiply by the grid spacing squared. This grid method works for any shape and achieves 5–10% accuracy, which is sufficient for most material estimation purposes.
Square feet (sq ft) measures a two-dimensional area — it accounts for both length and width. One square foot is a square measuring 1 ft × 1 ft. Linear feet (LF or lin ft) measures a single dimension of length — it has no width. Flooring and paint are measured in square feet. Baseboards, fencing, and gutters are measured in linear feet. The most common confusion: 500 linear feet of baseboard and 500 square feet of flooring are completely different quantities covering completely different material needs.
One acre = 43,560 square feet. This comes from the historical measurement of one furlong (660 feet) × one chain (66 feet) = 43,560 sq ft. Equivalently: an acre is approximately 209 ft × 209 ft as a square, or 217 feet × 200 feet as a rectangle. A football field (including end zones) is approximately 1.32 acres. A standard suburban lot of 0.25 acres = 10,890 sq ft — approximately 100 × 109 feet.
Area = π × r², where r is the radius (half the diameter). For a circular garden bed 12 feet in diameter: r = 6 ft, Area = 3.14159 × 36 = 113.1 sq ft. For an oval bed: Area = π × a × b, where a and b are the two half-axes. An oval 15 ft × 10 ft: a = 7.5, b = 5, Area = 3.14159 × 7.5 × 5 = 117.8 sq ft. Convert to cubic yards for soil orders: 113 sq ft × 0.25 ft deep ÷ 27 = 1.05 cubic yards.
Exterior footprint area: measure the outside dimensions of the house at ground level, calculate the total bounding rectangle, then add or subtract attached structures (garage, porch). Interior livable area: measure each room from finished wall to finished wall, calculate each area separately, and sum. Exclude closets for some definitions of livable area; include for others. For property lots: use the recorded legal description dimensions from the deed or survey, or use satellite mapping tools that show measured area directly.
In the US: square feet (sq ft) for rooms, buildings, and most materials. Square yards (sq yd) for carpet and some concrete. Cubic yards (yd³) for volumetric materials like concrete and gravel. Acres for land area. In the metric system: square meters (m²) for rooms and buildings, hectares for land. Many construction materials bridge both systems — roofing squares (100 sq ft), concrete ordered in cubic yards with area given in square feet, flooring quoted in square feet but sold in metric-sized tiles. Always confirm units when comparing quotes from different suppliers.