Square Footage Calculator (Rooms & Floors)
Room area for rectangles, L-shapes, circles, and triangles with a running project total, perimeter, and flooring cost per square foot in one pass.
Square Footage — interactive calculator, computed instantly in your browser.
Square Footage Made Easy: Measuring Rooms, L-Shapes, and Odd Floors
Rect A (12 × 10 = 120) + Rect B (6 × 4 = 24) = 144 ft²
Square footage answers the questions that come before every lease, tile order, and flooring quote: how big is this room, this floor, this lot? The calculator measures rectangles, L-shapes, circles, and triangles, keeps a running total across rooms in a project, and reports perimeter, alternate units, and material cost per square foot.
1. The Four Shapes
- Rectangle: 12 × 10 = 120 ft² — the workhorse of rooms and yards
- L-shape: cut the L into two rectangles and add: (12 × 10) + (6 × 4) = 144 ft²
- Circle: radius 6 ft → 3.1416 × 36 = 113.1 ft² (round patios, rug searches)
- Triangle: ½ × base × height — attic nooks and hip-roof floors
2. What to Include
- Rentals: measure wall-to-wall including closets — that is how usable square footage is counted
- Flooring purchases: add 10% for planks (cuts and mistakes), 15% for diagonal installs, 5% for carpet (it stretches)
- Subtract fixed islands or built-ins only when the material must flow around them
- Balconies and unfinished spaces count differently per listing rules — state your convention when publishing
3. From Square Feet to Other Units
- Flooring in metric is sold by m²: 144 ft² = 13.38 m²
- Carpet and tile quotes often arrive in square yards: 144 ft² = 16 yd²
- Land: 10,000 ft² is about 0.23 acres — the lot-size convention in US listings
- The project list sums every room you add so multi-room quotes need one pass, not a calculator tape
4. Costing the Floor
Enter your price per square foot — laminate runs roughly $2–5, engineered wood $4–10, tile $3–15 installed — and the calculator multiplies across the project total plus your waste margin. Material price and installed price differ by the labor line: get both quotes, then compare using the same waste-adjusted area so bids line up square-foot for square-foot.
🔗 Area Math Cross-References
Square footage is geometry with a lease attached — the raw area and unit math lives on the 🔄 Conversion Hub.
Floor area drives what you paint, what you pour, and what you pay: chain it into the material estimates below before quoting a project.
Frequently Asked Questions (Square Footage)
Measure length and width along the floor in feet, then multiply: a 12 × 10 room is 120 ft². For odd shapes, split the floor into rectangles, calculate each, and add them together — the L-shape mode in this calculator does exactly that with two length-width pairs.
Divide it into two rectangles along the inside corner. Measure each rectangle separately, multiply length by width, then add the areas: (12 × 10) + (6 × 4) = 120 + 24 = 144 ft². Never subtract a notch from a big bounding rectangle unless the missing piece is truly rectangular.
For rentals and listings, yes — closets count as usable floor area, measured wall-to-wall. For flooring orders, include closet floors if the material runs into them, then add the appropriate waste percentage (about 10% for planks) so cuts and mistakes are covered.
One square yard equals 9 square feet (3 ft × 3 ft). Carpet and some tile is priced per square yard: divide square feet by 9. A 120 ft² room is 13.33 yd² — always confirm which unit the quote uses before comparing bids.