Square Footage Calculator
Measure a room, a whole house, a lawn, or an oddly shaped patio and get the answer in seconds. Type in your length and width, add as many spaces as you need, and this square footage calculator adds them up for you. No mental math, no scribbling on the back of an envelope.
How to use the calculator
The core of it is one simple formula: length times width. Measure a rectangular space in feet, multiply the two numbers, and you have the area in square feet. A room that is 12 feet by 16 feet works out to 192 square feet. A 12 by 12 room is 144 square feet.
Most real spaces aren't a single clean rectangle, though, so the tool lets you add more than one area at a time. Break an L-shaped living room into two rectangles, enter each one, and the running total stacks them together. That's the same trick a contractor or an appraiser uses, and it's the fastest way to handle a floor plan with bump-outs, closets, and hallways.
A few things worth knowing as you go:
- Measure in the same unit throughout. If part of a wall is in inches, convert it before you multiply (divide inches by 12 to get feet).
- The results show up in square feet, square yards, and acres, so you can order flooring by the square yard or check a lot size against an acre without a second lookup.
- For circles and triangles, use the shape tools linked below instead of length times width. A round patio uses pi times the radius squared. A triangular corner uses base times height divided by two.
If you want the full walkthrough with diagrams and worked examples, the pillar guide on how to calculate square footage covers every shape and every conversion in detail.
All the calculators, by job
Square footage means something a little different depending on what you're buying. Flooring is priced by the square foot or square yard. Paint is sold by how many square feet a gallon covers. Concrete is ordered by the cubic yard. Pick the tool that matches your project.
Room and building calculators
- Room square footage calculator for a single room, including closets and alcoves.
- House square footage calculator for a whole home, floor by floor, using living-area rules.
- Roof square footage calculator that accounts for pitch, not just the footprint.
- Wall square footage calculator for drywall, wallpaper, and wall paint.
Material calculators
- Tile calculator with a waste factor for cuts and breakage.
- Flooring calculator for hardwood, laminate, vinyl, and carpet.
- Paint calculator that turns wall area into gallons.
- Concrete calculator for slabs, footings, and patios in cubic yards.
- Countertop calculator for kitchen and bath surfaces.
- Lawn and sod calculator for grass seed, sod, and fertilizer coverage.
Shape tools
Not everything is a rectangle. Use the triangle calculator for gables, corner lots, and angled rooms, and the circle calculator for round patios, garden beds, and above-ground pools.
Unit converters
- Square footage to acres for lots and land (1 acre is 43,560 square feet).
- Square inches to square feet when your measurements came off a tape in inches.
- Square feet to linear feet for trim, baseboard, and plank flooring.
- Square feet to cubic yards for mulch, gravel, and concrete depth.
- Square feet to square meters for metric plans and international listings.
Feet and inches
Measuring rarely lands on a round number. The feet and inches tool lets you enter dimensions like 12 feet 7 inches without converting the fractions in your head first.
How square footage is calculated
The whole system rests on one idea. A square foot is the area of a square that is one foot on every side, which is 144 square inches. Area is how many of those little squares fit inside a space. For a rectangle you multiply length by width, and the answer is the count of those one-foot squares.
That's why the units matter. Multiply feet by feet and you get square feet. Multiply an area in square yards by nine to get square feet, because a yard is three feet and three times three is nine. Multiply square meters by 10.764 to get square feet. Divide square inches by 144. Divide square feet by 43,560 for acres.
When a shape isn't rectangular, you break it into pieces you can measure, find the area of each, and add them up. Rooms become rectangles plus the odd triangle. A circle uses pi (about 3.14159) times the radius squared. A house is just every finished room added together, following a measurement standard so the number is consistent from one appraiser to the next. The full guide walks through each of these with real numbers, and what is a square foot explains the unit itself if you want to start from the ground up.
Frequently asked questions
How do you calculate square footage?
Multiply length by width for any rectangular space, with both measurements in feet. A 10 by 12 room is 120 square feet. For a space made of several rectangles, measure each one, multiply, and add the results together. For circles use pi times the radius squared, and for triangles use base times height divided by two.
What is the formula for square feet?
For a rectangle or square, area equals length times width. If you measured in inches, divide the result by 144 to convert to square feet. The calculator handles the multiplication and the unit conversion for you, but the formula underneath is that simple.
Is this a free online square footage calculator?
Yes. The tool runs in your browser at no cost, with no sign-up. Enter your dimensions, add as many areas as your project needs, and read the total in square feet, square yards, and acres.
Can I add up more than one room at once?
That's what the total square footage calculator is built for. Add each room or section as its own entry and the running total combines them. It's the right approach for a whole house, an L-shaped room, or a floor plan with several distinct spaces.
How do I measure a room that isn't a perfect rectangle?
Split it into rectangles and, where needed, triangles. Measure and calculate each piece, then add them together. This is the standard method for bay windows, bump-outs, and angled walls, and it's covered step by step in the how to calculate square footage guide.