Square Footage Calculator – Rooms, L-Shapes, Circles, and Cost
Our free square footage calculator works out the area of any room, yard, or project in square feet, square yards, and square meters. Add rectangles, L-shaped rooms, circles, triangles, and trapezoids, subtract the parts you skip, and enter a price per square foot to see the cost of flooring, paint prep, sod, or any other material sold by area. Copy the result or print it for the store.
How to Use the Square Footage Calculator
All you need is a tape measure, a notepad, and a rough sketch of the space:
- Pick a shape. Each area can be a rectangle, an L-shape, a circle, a triangle, or a trapezoid. The fields change with the shape.
- Enter the sizes. Type feet as 12.5, 12 1/2, or 12’6″ for 12 feet 6 inches. Switch to metric if you measure in meters.
- Add every room. Tap “Add another room or area” for each space. The calculator adds them all up, and you can give each one a name, such as “Kitchen” or “Hall.”
- Subtract what you skip. A kitchen island, a fireplace hearth, or a built-in closet gets its own area with the box “Subtract this area” checked.
- Add extra and a price. Enter the extra you need for cuts, and a price per square foot or per square yard, and the calculator shows the area to buy and the cost.
- Copy or print. The list with all rooms, sizes, and totals goes to your clipboard or prints on US Letter or A4.
How to Calculate Square Footage
Square footage is the area of a flat surface, measured in squares that are 1 foot on each side. For a rectangle, you multiply the length by the width. A room that is 12 feet long and 10 feet wide has 12 × 10 = 120 square feet.
The most common mistake is mixing feet and inches. 12 feet 6 inches is 12.5 feet, not 12.6 feet, because a foot has 12 inches. Convert the inches first (6 ÷ 12 = 0.5), or type 12’6″ into the calculator and let it do the conversion.
These are the formulas the calculator uses:
| Shape | Formula | Example |
|---|---|---|
| Rectangle or square | length × width | 12 × 10 ft = 120 sq ft |
| L-shape | (length 1 × width 1) + (length 2 × width 2) | 15 × 10 + 8 × 6 ft = 198 sq ft |
| Circle | π × radius², radius = diameter ÷ 2 | 10 ft across = 78.5 sq ft |
| Triangle | base × height ÷ 2 | 10 ft base, 8 ft high = 40 sq ft |
| Trapezoid | (side a + side b) ÷ 2 × height | (12 + 8) ÷ 2 × 6 ft = 60 sq ft |
Example: a 12 × 10 Bedroom
A bedroom that measures 12 by 10 feet has 120 square feet. In square yards, that is 120 ÷ 9 = 13.33 square yards, and in square meters 120 × 0.0929 = 11.15 square meters. If you buy laminate with 10% extra for cuts, you need 132 square feet of flooring.
Example: an L-Shaped Living Room
Split the L into two rectangles that do not overlap. A living area of 15 × 10 feet with a dining nook of 8 × 6 feet is 150 + 48 = 198 square feet. Together with the 120 square foot bedroom, the total is 318 square feet. With 10% extra, you buy 349.8 square feet, and at $3.50 per square foot, the flooring costs $1,224.30.
Square Feet, Square Yards, and Square Meters
Different trades use different units. Flooring and tile are usually priced per square foot, carpet often per square yard, and anything from Europe or Canada in square meters. These are the exact conversions:
| Unit | In square feet | In square meters |
|---|---|---|
| 1 square foot | 1 | 0.0929 |
| 1 square yard | 9 | 0.8361 |
| 1 square meter | 10.764 | 1 |
| 1 acre | 43,560 | 4,046.86 |
A square yard is 3 × 3 feet, which is why you divide square feet by 9 and not by 3. The calculator also shows acres, which helps with lawns, fields, and lot sizes.
How to Measure a Room
Good numbers start with good measuring. A few habits save you from buying too little:
- Measure wall to wall at floor level. Baseboards are thin, so measure from wall to wall, not from trim to trim.
- Measure twice in different spots. Old houses are rarely square. Use the longer number of each pair.
- Sketch the room first. Draw the outline on paper and split odd shapes into rectangles and triangles before you measure.
- Include closets and doorways if the flooring runs into them. Leave out the space under kitchen cabinets and fixed islands.
- Round up, not down. If a wall is 11 feet 7 inches, 11.6 feet is fine. The extra percentage takes care of the rest.
If you are planning to paint, the floor area is only the start. In a small or medium room with 8 foot ceilings, the walls are roughly two to three times the floor area; in large rooms the factor is lower, so measure the walls too. Our guide to the standard ceiling height gives you the typical numbers, and paint can sizes helps you buy the right amount.
How Much Extra Should You Add?
Most materials are cut to fit, and the offcuts at the walls are lost. These are common starting points. The product instructions always come first.
| Material | Typical extra |
|---|---|
| Laminate and vinyl plank, straight | 5 to 10% |
| Hardwood, straight | 10% |
| Tile, straight layout | 10% |
| Tile or wood, diagonal or herringbone | 15 to 20% |
| Carpet | 10% or more, depending on the roll width and seams |
| Sod and landscape fabric | 5 to 10% |
The calculator adds the extra only to the area you buy. The total area stays the real area of the room, so you can compare it with a listing or an appraisal.
What Square Footage Is Used For
The same number shows up in many projects around the house:
- Flooring: laminate, vinyl, and hardwood are sold in boxes that cover a set number of square feet. Divide your area with extra by the coverage per box and round up. If you refinish a floor instead, see our guide to the best polyurethane for floors.
- Painting floors: paint and coatings list their coverage in square feet per gallon. Our article on how to paint laminate flooring shows the steps.
- Time planning: painters and flooring crews often quote by area. Our guide on how long it takes to paint a room gives you realistic times.
- Lawns and patios: sod, seed, pavers, and landscape fabric are all priced by area.
- Heating and cooling: the size of a heater or an air conditioner depends on the floor area of the room.
Privacy and Honest Limits
The square footage calculator runs entirely in your browser. There is no sign-up, and nothing you enter is sent anywhere. It measures flat areas only. For sloped ceilings, stairs, or walls, measure each surface as its own shape. Official square footage for a home sale follows its own rules, such as the ANSI measuring standard many appraisers use, so a listing can show a different number than your floor plan.
More Free DIY Tools
All our tools are free, run in your browser, and need no account.
- Concrete Calculator: work out cubic yards and bags of concrete for slabs, footings, and posts.
- Board Foot Calculator: turn your cut list into board feet and lumber cost.
- Paint Calculator: find out how many gallons of paint your room needs.
- Tile Calculator: count the tiles, boxes, and grout for your floor or wall.
- Wallpaper Calculator: see how many rolls of wallpaper you need.
Frequently Asked Questions
How Do I Calculate the Square Footage of a Room?
Measure the length and the width in feet and multiply them. A 12 × 10 ft room has 120 square feet. For odd shapes, split the room into rectangles and add the parts.
How Do I Convert Inches to Feet for Square Footage?
Divide the inches by 12 before you multiply. 10 feet 6 inches is 10.5 feet. If you measure everything in inches, multiply the two numbers and divide by 144, because a square foot has 144 square inches.
How Many Square Feet Are in a Square Yard?
There are 9 square feet in a square yard, because a yard is 3 feet and 3 × 3 = 9. To turn square feet into square yards, divide by 9.
How Do I Find the Square Footage of an L-Shaped Room?
Split the L into two rectangles that do not overlap, work out each area, and add them. 15 × 10 ft plus 8 × 6 ft is 150 + 48 = 198 square feet.
How Do I Calculate the Area of a Circle in Square Feet?
Halve the diameter to get the radius, square it, and multiply by π (3.1416). A round patio that is 10 feet across has 5 × 5 × 3.1416 = 78.5 square feet.
How Much Extra Flooring Should I Buy?
For a straight layout, 5 to 10% is common. Diagonal and herringbone patterns need 15 to 20%. Keep one unopened box for repairs later.
How Do I Calculate the Cost per Square Foot?
Multiply the area you buy by the price per square foot. 349.8 square feet at $3.50 is $1,224.30. The calculator does this for you and also accepts a price per square yard.
Is the Square Footage Calculator Free?
Yes. It is free, needs no account, works in feet or meters, and lets you copy or print the result.
Robert Thompson has worked as a self-employed carpenter for over 15 years. He lives with his family in Billings, Montana, where he also successfully operates his business as a woodworker. His main business is the complete interior construction of buildings. He is also passionate about creating high-quality wood furniture with epoxy and other items made from burl wood. Besides the woodwork, Robert is also a skilled DIY professional for all kinds of materials. He always has a solution ready for every craft and construction challenge. Originally, Robert studied civil engineering and has advanced degrees in carpentry and business management. Robert has been working for Craft Art since 2020 and enriches the blog with his immense knowledge and skills in the field of woodworking and home improvement. He writes the articles about DIY and Repair.
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