Square Footage Calculator
Planning a remodel? Pricing new floors? Estimating paint? You’ll need rock-solid area numbers before you buy anything. This square footage calculator turns widths and lengths into usable totals in seconds, then converts units and even estimates cost. The math is simple and the results are reliable.
How the calculator works
You enter width and length for a rectangle then select your unit. Add a quantity if you have identical spaces. The tool multiplies width × length × quantity to get total area. Want other shapes? Use the shape formulas below or split the space into rectangles and triangles. That approach mirrors how contractors estimate rooms on site because it’s fast and accurate.
After the area appears you can change the output unit. The converter updates in real time. If you enable pricing, the calculator multiplies the area by your price per unit to show a total cost. Simple inputs lead to fast decisions.
What is square footage?
Square footage measures area in square feet (ft²). One square foot equals an area 1 foot by 1 foot. Many countries use square meters (m²) for the same idea. The two tie together by a fixed conversion rate based on the definition of the foot and the meter.
| Unit | Symbol | In square feet | In square meters |
|---|---|---|---|
| Square foot | ft² | 1 | 0.09290304 |
| Square yard | yd² | 9 | 0.83612736 |
| Square inch | in² | 0.006944444 | 0.00064516 |
| Square meter | m² | 10.7639104167 | 1 |
| Square centimeter | cm² | 0.001076391 | 0.0001 |
Those constants trace back to the modern definitions of the foot and meter. If you enjoy digging into standards, see the entries for the foot and the meter.
Formulas by shape
Rooms rarely stay perfect rectangles. You might have a bay window or an angled entry. Use the formulas below for clean shapes. For odd rooms split the space into a combination of these shapes then add the areas.
Rectangle or square
Formula: Area = width × length
Triangle
Formula: Area = 0.5 × base × height
Use height at a right angle to the base. If you don’t have it, draw a perpendicular line or compute height from other sides using trigonometry.
Circle
Formula: Area = π × r² or Area = 0.785398163 × d²
Measure radius r or diameter d. Circular foyers and hot tubs pop up more than you’d think.
Trapezoid (two parallel sides)
Formula: Area = (a + b) ÷ 2 × h
Here a and b are the lengths of the parallel sides and h is the perpendicular height. Great for angled walls.
L-shaped room
Split the footprint into two rectangles. Compute both then add the results. That’s not only simple, it mirrors how installers order materials.
Curved alcoves and cutouts
Approximate the curve with a simple shape. A half circle uses 0.5 × π × r². A quarter circle uses 0.25 × π × r². Add or subtract from the main rectangle as needed.
How to measure accurately
A good measurement saves money because you buy the right amount of material once. Here’s a field-tested process that works.
- Clear a path. Move chairs and small items. You want the tape flat against the baseboard or floor.
- Pick a datum. Start in one corner and move clockwise. Consistency keeps notes clean.
- Measure long walls first. Record to the nearest 1/8 in or 0.5 cm. Tight tolerances reduce rounding drift.
- Note protrusions and openings. Bay windows, alcoves, fireplaces and stair cutouts change totals.
- Sketch as you go. Draw a quick plan with lengths beside each wall. Future you will say thanks.
- Confirm squareness. If diagonals differ by more than 1 inch in a 12′ room the room isn’t square. Expect trimming waste for rigid materials.
- Enter numbers in the calculator. Calculate each section then sum totals.
Need to measure a busy space like a kitchen with islands? Break it into obvious rectangles. Measure around fixed cabinets instead of pushing a tape under them. That habit reflects how floors are actually installed.
Feet-and-inches and metric conversions
Homes often mix feet and inches. Don’t worry. Convert everything to a single base unit before you multiply.
| Conversion | Exact factor | Tip |
|---|---|---|
| 1 ft | 12 in | 12 inches make a foot |
| 1 m | 100 cm | Move the decimal two places |
| 1 m | 3.280839895 ft | Multiply meters by 3.28084 for feet |
| 1 m² | 10.7639104167 ft² | Multiply by 10.764 for quick mental math |
Feet and inches example
Let’s say a room measures 12 ft 7 in by 10 ft 4 in. Convert each side to feet then multiply.
- 12 ft 7 in = 12 + 7/12 = 12.5833 ft
- 10 ft 4 in = 10 + 4/12 = 10.3333 ft
- Area = 12.5833 × 10.3333 = 130.1 ft² (rounded)
Metric example
A balcony measures 3.4 m by 1.2 m. Area equals 4.08 m². Convert to ft² with the factor above if a vendor quotes in imperial.
Cost estimation from square footage
Once you know the area you can attach a cost per unit. That’s helpful for flooring, turf, tile, paint coverage, and wallpaper. Most products quote pricing either per square foot or per square meter. The calculator multiplies for you.
Waste factors
Real jobs need extra material for offcuts and pattern matching. How much extra depends on the material and the layout.
- Laminate or vinyl plank: 5–7% in simple rooms. 8–10% with many doors or angles.
- Tile: 10–15% if diagonal or large format tiles intersect many walls.
- Carpet: Often driven by roll widths and seam layout. Ask your installer for a cut plan.
- Paint: One gallon covers roughly 350–400 ft² per coat on smooth walls. Porous surfaces need more.
Add the waste percentage after you compute the raw area. It’s better to return a spare box than to pause a project for one more carton.
Worked examples
Example 1 — Simple bedroom
You measure 11 ft 6 in by 13 ft 0 in. Convert to feet.
- 11 ft 6 in = 11.5 ft
- 13 ft 0 in = 13 ft
- Area = 11.5 × 13 = 149.5 ft²
- Floor price = $3.49 per ft² → $521.76 for material
- Add 7% waste → 149.5 × 1.07 = 159.0 ft² → $554.91
Example 2 — L-shaped living room
Break the space into two rectangles. A = 12′ × 10′. B = 8′ × 6′.
- Area A = 120 ft²
- Area B = 48 ft²
- Total = 168 ft²
- At $2.80 per ft² the cost equals $470.40
Example 3 — Patio with a semicircle
The main rectangle is 18′ × 12′. A half circle with radius 6′ extends from one short side.
- Rectangle = 216 ft²
- Semicircle = 0.5 × π × 6² ≈ 56.55 ft²
- Total ≈ 272.55 ft²
Pro tips and common mistakes
- Use consistent units. Convert before you multiply. Switching mid-calculation skews results.
- Measure baseboard-to-baseboard for floors. Drywall can bow slightly. The baseboard gives a consistent reference.
- Record decimals not mixed fractions. Decimals reduce mistakes when you re-enter values.
- Check for out-of-square rooms. Large diagonal differences point to trapezoidal shapes. Use trapezoid math or split the room.
- Don’t forget closets and niches. Small spaces add up. Measure them while you’re there.
- Price for installed coverage. If a product has a mandatory overlap or grout joint, use the effective coverage per unit from the data sheet.
FAQ
How do I convert square feet to square meters?
Multiply by 0.09290304. For the reverse multiply by 10.7639104167. Those factors come from the exact relationship between the foot and the meter.
What’s the easiest way to measure an odd room?
Split it into rectangles and triangles. Compute each then add. That keeps math easy and matches how installers think about material layouts.
Should I include doorways?
For flooring yes because the material continues through the opening. For paint no because doors reduce paintable wall area.
How accurate should I be?
Measure to the nearest 1/8 inch or 0.5 cm. Round final totals to the precision your vendor uses. Add a waste factor for cuts.
Can I use the calculator for walls and ceilings?
Absolutely. Measure height and length for each wall then multiply. Subtract large windows if needed. For ceilings treat them like floors.
Further reading
- Definition of the foot and historical notes — Wikipedia: Foot (unit)
- Definition of the meter — Wikipedia: Metre
- Interior paint coverage basics — U.S. EPA: Paints and Coatings
- Need to estimate bulk materials by volume? Try our Sand Calculator next.
How to use this Square Footage Calculator effectively
You’ll get the best results if you follow a short routine.
- Select your preferred unit set. If you measure in feet and inches choose the ft/in option so you can enter both directly.
- Measure width and length. Use decimals for inches when you can. 7⅝ inches becomes 7.625 inches.
- Enter a quantity if you have identical areas. Apartment units or repeated hallway sections use this well.
- Pick the output unit you want. Contractors often prefer ft² while building codes and material data sheets sometimes quote m².
- Turn on pricing. Type your price per ft² or per m². The calculator shows the project total instantly.
Unit glossary
Not sure what symbols mean at a glance? This quick glossary helps.
- ft = foot (length)
- in = inch (length)
- m = meter (length)
- cm = centimeter (length)
- ft² = square foot (area)
- m² = square meter (area)
- yd² = square yard (area)
- in² = square inch (area)
When to switch between ft² and m²
If your suppliers list metric coverage then set the output to m². If your crew measures with tape lines in feet then you’ll likely keep ft². Either choice is fine because the converter preserves accuracy.
Advanced notes for power users
Large commercial spaces sometimes need survey-grade precision. In those cases measure with a laser distance meter that logs points to a drawing app. Many modern devices export directly to CAD or BIM. Your square footage then becomes part of a clean digital model.
If you manage warehouses, divide the plan into measured zones and label every zone with an ID. You can tie the calculator totals to those IDs so orders match the layout on delivery day. That simple habit saves returns and confusion.
Common materials and typical coverage
| Material | Sold as | Typical coverage | Notes |
|---|---|---|---|
| Luxury vinyl plank | ft² per carton | 18–28 ft² | Allow 5–7% waste. More with complex rooms. |
| Ceramic tile | ft² per box | Varies by tile size | Use 10–15% waste if laid on a diagonal. |
| Carpet | yd² or ft² | 12 ft roll width is common | Seam planning determines waste more than shape. |
| Paint | gallons | 350–400 ft² per coat | Coverage depends on substrate and color. |
Troubleshooting odd results
If the area looks off by a factor of ten then the culprit is usually mixed units. Convert inches to feet or centimeters to meters before multiplying. Check that you didn’t enter millimeters where centimeters belonged. It happens.
If a room isn’t close to rectangular then a single rectangle will overstate totals. Split the shape. Use a triangle for angled corners and a semicircle for round bays. The error disappears once you compute each piece separately.
Related tools
- Working with loose materials by volume? Try our Sand Calculator.
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