How to Use This Calculator
Choose your shape from the tabs. Rectangle handles most rooms and floors. Circle covers round patios, pools, and planting areas. Triangle works for angled roof sections or odd corners. Input units default to feet; switch to inches, yards, or meters if that's how your measurements are written. The Quantity field multiplies one room's area across several identical spaces, which saves steps when ordering flooring for multiple bedrooms of the same size. Enter a material price to get an exact cost estimate alongside the standard range. For L-shaped rooms, use the calculator twice, once per rectangle, and add the results.
How to Calculate Square Footage
Multiply length by width. That's the whole formula: Square Feet = Length × Width.
A 12 × 15 bedroom is 180 square feet. Ordering flooring? Add 10% for waste: 180 × 1.10 = 198 square feet to purchase. Tile with a diagonal pattern, or a room with lots of cuts around fixtures and islands? Use 15% instead. That extra material will get used.
Carpet is sold by the square yard at most retailers. Divide your square footage by 9. That same 180-square-foot bedroom is 20 square yards. Ask whether your retailer quotes in square feet or square yards before comparing prices. The unit varies by store and the same room can look like two different numbers.
For L-shaped rooms, calculate the full outer rectangle and subtract the missing piece. A space that measures 20 × 15 overall with a 5 × 10 corner removed is (20 × 15) − (5 × 10) = 300 − 50 = 250 square feet. Sketch it on paper first. One wrong measurement in an irregular room is a costly ordering mistake.
Square Footage Tips
Measure in at least two places. Rooms in older homes are rarely perfectly square, and walls bow more than you'd expect. Measure length near both ends of the room and use the larger number. Coming up short on flooring mid-project means a second order, a second delivery charge, and material from a different production batch that may not match.
Increase your waste factor to 15% for rooms with lots of cuts: kitchens with islands, bathrooms with offset toilets, rooms with non-90-degree angles. The difference between 10% and 15% on a 200 sq ft room is roughly one extra box of flooring. Running short and special-ordering a partial box costs far more.
When ordering hardwood or tile, buy all material from the same production batch. Batch numbers appear on box labels. Colors and textures vary between production runs and cannot always be matched after the fact. Buy one extra box as a permanent repair buffer. One cracked tile or scratched plank is nearly inevitable over a floor's lifetime.
For carpet, know whether your retailer quotes in square yards or square feet before you call. A 200 sq ft bedroom is 22.2 square yards. Always round up to the next full yard. Getting the unit wrong when comparing quotes from two stores is a common and expensive mistake.
What to Buy
For laminate and engineered hardwood, major brands like Pergo and Armstrong sell by the carton, each covering roughly 20 square feet. Calculate your total with waste included, divide by carton coverage to find how many you need, then buy one extra. If a plank needs replacing in five years and the product is discontinued, matching color and texture from a different production run is extremely difficult.
For carpet, Shaw and Mohawk are the two largest residential brands and both sell by the square yard. Home Depot and Lowe's quote carpet by the square foot at checkout, but warehouse fulfillment is in square yards. Know which unit you're working in when comparing quotes from multiple retailers.
For interior paint, one gallon of Sherwin-Williams or Benjamin Moore covers approximately 350 square feet of wall per coat. Calculate wall area separately: height × perimeter, not floor square footage. A 12 × 14 room with 9-foot ceilings has about 468 square feet of wall. Two coats takes roughly 2.5 to 3 gallons, plus primer if you're covering a dark color or raw drywall.