Square Footage Calculator: Measure Rooms, Walls & Land
Use this free square footage calculator to measure any room, wall, or outdoor space in seconds. Enter the dimensions, choose the shape, and get an instant area calculation for flooring, paint, tile, landscaping, or a real-estate listing. The calculator works in feet, inches, meters, and yards, and handles rectangles, circles, triangles, and irregular layouts.
What Is Square Footage?
Square footage is the total area of a space, expressed in square feet. It’s calculated by multiplying length by width for a rectangular space, or using the matching formula for other shapes. Square footage is the standard unit contractors, real-estate listings, and building codes use to describe the size of a room, wall, or lot.
How to Use This Calculator
Pick the shape that matches your space — rectangle, circle, triangle, or an irregular layout you can split into parts.
Enter your measurements in whichever unit is on your tape measure. The calculator converts as needed.
If you’re pricing a project, add the price per square foot to see the total cost.
For a whole home or a floor with several rooms, calculate each room and add the results together.
The Formulas Behind the Calculator
You don’t have to do the math yourself, but knowing the formula helps when a room doesn’t fit one clean shape.
Rectangle or Square
Length × width. A 12 ft × 15 ft bedroom is 180 square feet. This covers most rooms in a typical home.
Triangle
½ × base × height. Height is the perpendicular distance from the base to the opposite point — not the length of a slanted side. For a right triangle, the two legs are the base and height.
Circle
π × radius². For a round patio 10 ft across, the radius is 5 ft, so the area is 3.1416 × 25 = about 78.5 sq ft. Measure the diameter (widest point across) and divide by two to get the radius.
Trapezoid
½ × (side a + side b) × height, where side a and side b are the two parallel sides and height is the perpendicular distance between them.
L-Shape or Irregular Room
Split the room into rectangles, calculate each one, and add them together. A bay window or alcove becomes its own small rectangle. Anything with a curve can be approximated with a circle segment or a series of thin rectangles. See our irregular-shape square footage calculator for a step-by-step tool.
Measuring an Irregular or L-Shaped Room
Sketch the room on paper. Draw straight lines to divide it into rectangles, plus triangles if there’s a diagonal wall. Measure each shape, calculate its area, and add the results together. A bay window or alcove is its own small rectangle. Closets count when you’re ordering flooring — they don’t always count for real-estate square footage rules.
For a room with a sloped ceiling, the floor area doesn’t change. If you’re painting or drywalling the slope, measure it separately using the slant length, not the horizontal distance across the room.
Measuring for Common Projects
Cost per Square Foot by Project Type
Actual costs vary by region, material grade, and installer, but these ranges are a useful starting point for budgeting a project:
| Project | Average Cost per Sq Ft |
| Hardwood flooring | $8 – $14 |
| Tile | $3 – $12 |
| Paint | $2 – $4 |
Flooring — Tile, Vinyl Plank, Hardwood, Laminate
Measure length × width of each room. Add 10% for cuts and waste on straight-lay patterns, or 15% for diagonal and herringbone layouts. Order full boxes rather than the exact square footage — you’ll want extras from the same dye lot for future repairs. Our tile & flooring square footage calculator handles the waste percentage for you.
Carpet
Measure the room, then check the roll width — usually 12 feet. Rooms wider than 12 feet require a seam. This means you’ll need to order the length of the room multiplied by the number of 12-ft strips needed to cover the width. For example, a 15 ft × 20 ft room needs two 12-ft strips, so you order 40 linear feet of 12-ft-wide carpet (20 ft × 2), not just 300 sq ft. Add about 10% for waste.
Paint
Add up the length of every wall to get the perimeter, then multiply by the ceiling height. Subtract roughly 20 sq ft for each door and 15 sq ft for each average window. One gallon covers about 350 to 400 square feet with one coat, so plan for two coats on new drywall or a dramatic color change. If you’re only painting one wall, use the wall square footage calculator or jump straight to the paint calculator to get gallons.
Wallpaper
Same wall measurement as paint, but check the roll’s usable square footage on the label — it’s always less than the raw roll size because of pattern repeats. Order an extra roll from the same batch for repairs.
Backsplash and Shower Tile
Measure height × width of each tiled surface separately. For showers, include the ceiling if you’re tiling it and subtract the door opening. Small mosaic sheets waste less than large-format tile. For counters and shower walls specifically, use the countertop & shower square footage calculator.
Landscaping — Sod, Mulch, Gravel, Pavers
Measure the area you’re covering. Mulch and gravel are sold by cubic yard or cubic foot, so multiply square footage by the depth in feet to get cubic feet, then divide by 27 for cubic yards. A 3-inch mulch layer over 100 sq ft is about 1 cubic yard. For lawns, our lawn & sod square footage calculator converts your yard directly into pallets or rolls.
HVAC Sizing
Total the finished, conditioned square footage of the home. A rough starting point is 20 BTU per square foot for cooling. A 1,500 sq ft home would need about 30,000 BTU (2.5 tons). This is only a starting point — climate, insulation, ceiling height, and window area all shift the real number, so use the square footage as an input for a proper Manual J load calculation, not as the final answer.
Real Estate
For a listing, most regions in the US follow the ANSI Z765 standard: measure the exterior of the home and count only finished, heated space. Basements, garages, and unfinished attics are reported separately. Rules vary by MLS and country, so check local guidance before publishing a number.
House Calculation Rules (ANSI Standard)
For a single-story rectangular home, it’s exterior length × exterior width, minus any open areas like a two-story foyer. For multi-story homes, calculate each floor’s finished area and add them. Garages, unfinished basements, screened porches, and attics without heating and finishing are excluded from the “finished square footage” figure that most appraisers and MLS listings use, though they’re often disclosed separately. For the exterior envelope, our roof square footage calculator and drywall, siding & brick calculator cover the surfaces above and around the floor plan.
Unit Conversions Worth Knowing
Square Footage vs. Square Meters
Square feet are standard in the US, while most of the rest of the world measures area in square meters. Use square meters when you’re working from an international floor plan, buying imported flooring or tile sold by the square meter, or listing a property in a country that uses the metric system. Otherwise, square feet is the safer default for US contractors, retailers, and MLS listings.
- 1 square foot = 0.0929 square meters
- 1 square meter = 10.764 square feet
- 1 square yard = 9 square feet
- 1 acre = 43,560 square feet
- 1 hectare = 107,639 square feet
If you measured in inches, divide the total square inches by 144 to get square feet. If you measured in centimeters, divide the total square centimeters by 929.
Common Mistakes to Avoid
- Measuring to the outside of baseboards instead of the actual wall line, which can overstate a room’s area.
- Forgetting to include closet space when ordering flooring, even though it’s sometimes excluded from real-estate square footage.
- Using the slant length of a sloped ceiling instead of the horizontal floor area when calculating floor square footage.
- Confusing square feet with linear feet — baseboards, trim, and countertops are priced by linear foot, not area.
- Skipping the waste percentage on flooring, tile, or wallpaper orders and coming up short mid-project.
Frequently Asked Questions
How do I calculate square footage from a floor plan?
Use the scale printed on the plan — for example, ¼ inch = 1 foot. Measure each room in inches on the plan, convert to feet using the scale, then multiply length × width. Digital floor plans usually have a scale bar you can drag across, or a built-in area tool.
Do closets count as square footage?
For flooring, paint, and tile — yes, you have to cover them. For a real-estate listing, closets inside a bedroom usually count as part of the finished area; standalone storage rooms often don’t. Local rules apply.
What’s the difference between square feet and linear feet?
Square feet measure area (length × width). Linear feet measure length only. Baseboards, trim, countertops, and gutters are priced by linear foot. Flooring, paint, tile, and wallpaper are priced by square foot.
How much extra should I order for flooring?
Add 10% for straight-lay installation, 15% for diagonal patterns, and 20% if you’re tiling a room with many corners or cutouts. Always round up to the nearest full box.
Can I measure square footage from Google Maps?
For outdoor spaces — lawns, plots of land, roof outlines — yes. Google Earth Pro has a built-in area tool that lets you trace the perimeter and read the square footage. It’s fine for estimates, but the accuracy depends on the imagery date and how cleanly you can trace edges, so it isn’t a substitute for a tape measure on construction jobs or legal filings.
How do I calculate square footage in inches?
Measure length × width in inches, then divide the result by 144 to convert square inches to square feet. A 60 in × 30 in vanity top is 1,800 sq in, or 12.5 sq ft. For a dedicated tool, try the square footage calculator (feet and inches).
