Need the square footage of a room, a floor or your whole house? This free square footage calculator measures rectangles, L-shaped rooms, triangles, circles and trapezoids, adds several rooms together, and converts the total to square meters, square yards and acres. It also adds a waste allowance and tells you how many boxes of flooring, tile or carpet to buy and what it will cost.
Square Footage Calculator
Add any room shape, convert units and work out flooring boxes and cost.
Measure each room wall to wall at floor level. Split odd-shaped rooms into rectangles, triangles or circles and add them together.
How to Use the Square Footage Calculator
- Choose your unit (feet, meters, inches or yards) at the top.
- Pick the shape of the first room and enter its measurements.
- Click “Add another room or area” for every extra room or section.
- Choose a waste allowance for the material you are installing.
- Enter the price and box coverage to see how many boxes to buy and the total cost.
How to Calculate Square Footage
Square footage is the area of a flat surface measured in square feet. For a rectangle or square room:
Square feet = length (ft) × width (ft)
Example: an 18 ft by 14 ft living room is 18 × 14 = 252 sq ft. Add a 10 × 4 ft hallway (40 sq ft) and the total is 292 sq ft.
Square Footage Formulas for Every Shape
| Shape | Formula | Example |
|---|---|---|
| Rectangle / square | Length × width | 12 × 10 = 120 sq ft |
| L-shaped room | (A length × A width) + (B length × B width) | (15 × 10) + (6 × 6) = 186 sq ft |
| Triangle | Base × height ÷ 2 | 10 × 8 ÷ 2 = 40 sq ft |
| Circle | π × (diameter ÷ 2)² | 10 ft circle = 78.5 sq ft |
| Trapezoid | (Top + bottom) ÷ 2 × height | (8 + 12) ÷ 2 × 10 = 100 sq ft |
Unit Conversions
| Convert | Multiply by |
|---|---|
| Square feet to square meters | 0.0929 |
| Square meters to square feet | 10.764 |
| Square feet to square yards | 0.1111 (divide by 9) |
| Square inches to square feet | divide by 144 |
| Square feet to acres | divide by 43,560 |
How Much Extra Flooring Should I Buy?
- 5% for carpet, sheet vinyl or simple straight layouts in square rooms.
- 10% for laminate, vinyl plank, hardwood and standard tile.
- 15% or more for diagonal, herringbone or chevron patterns, and rooms with lots of corners.
Keep one or two spare boxes from the same batch for future repairs, because colors can vary between production runs.
Measuring Tips
- Measure wall to wall at floor level, ignoring baseboards.
- Round each measurement up to the nearest inch (or centimeter).
- Include closets and spaces under appliances if the flooring goes there.
- Planning to paint too? Our paint calculator works out the gallons for the same room.
Frequently Asked Questions
How do I calculate the square footage of a room?
Measure the length and width of the room in feet and multiply them. A 12 ft by 15 ft room is 180 sq ft. For odd shapes, split the room into rectangles and add them together.
How many square feet is a 12×12 room?
A 12×12 room is 144 square feet, which is about 13.4 square meters or 16 square yards.
How do I convert square meters to square feet?
Multiply square meters by 10.764. For example, 20 m² equals about 215 sq ft.
How do I calculate square footage of an L-shaped room?
Divide the L into two rectangles, find the area of each (length x width), and add them. The calculator’s L-shape option does this for you.
How many boxes of flooring do I need?
Divide the total area plus waste (usually 10%) by the coverage printed on one box, then round up. 300 sq ft with 10% waste is 330 sq ft; at 20 sq ft per box you need 17 boxes.
More Free Home Calculators
- Paint Calculator – how many gallons of paint a room needs
- Smart Home Cost Calculator – budget for a full smart home setup
- Lumens Calculator – how many bulbs and lumens each room needs
- AC BTU Calculator – find the right air conditioner size for any room
- Power Station Runtime Calculator – how long a battery backup will run your devices
