Square Footage Calculator
Enter your measurements in feet and inches or metric units. Calculate one or more rooms or areas, and add or subtract sections as needed. You can also estimate material quantities and material cost.
Calculate a room or area
How to calculate square footage
Square footage measures area. One square foot is the area of a square that is 1 foot long and 1 foot wide.
For a rectangle, multiply its length by its width. Use feet for both measurements to get square feet.
Area in square feet = length in feet × width in feet
A room measuring 12 ft × 10 ft = 120 sq ft. If you measure in meters, the same multiplication gives square meters. The calculator also accepts cm and mm, and shows their area in m².
Measurements use matching units before each shape formula is applied. Sections are added or subtracted within their room or area; material waste and box rounding are calculated separately.
Calculate your areaHow to measure a room
- Sketch the area. Mark corners and any separate sections. You can measure a whole room, just its floor, or an individual wall.
- Measure the boundaries. For a rectangular floor, measure length A and width B. For a wall, measure width and height.
- Record each measurement. Use the same units for each edge, then check the labels against the drawing. Split more complex areas into sections that do not overlap.
Diagrams show which edges to measure; they are not scale floor plans or cutting layouts.
Calculate square footage with feet and inches
Convert the inches in each measurement to a fraction of a foot before multiplying. Divide inches by 12, then add the whole feet.
12 ft 6 in = 12 + 6 ÷ 12 = 12.5 ft
12.5 ft × 10 ft = 125 sq ft
In the calculator, enter 12 in the ft box and 6 in the in box for the first measurement. Enter 10 ft for the second. The calculator handles the conversion.
- For inches only, leave ft blank.
- For decimal feet, choose Feet (ft) for a single input, such as 12.5. In ft + in mode, leave in blank or enter 0 when using decimal feet.
- For fractional inches, enter a value such as 6 1/2 in.
Example measurements are separate from your own.
Calculate L-shaped rooms and other irregular areas
L-shaped rooms: subtract the missing corner
Measure the full outside length A and width B. Then measure the two inside edges of the missing corner: C across the notch, and D down the notch.
Area = A × B − C × D
For example, 20 ft × 15 ft − 6 ft × 8 ft = 252 sq ft.
The L-shaped option already removes that corner. Add a subtracted section only for something else you want to leave out.
Add or subtract sections within an area
Use Add section for an extra part that belongs in the measurement, such as an alcove. Use Subtract section for a part you are leaving out, such as a column footprint or an opening in a wall.
Net area = main area + added sections − subtracted sections
Each section belongs to its own room or area. Avoid overlapping added sections. The calculator cannot detect overlaps from dimensions alone.
Example measurements are separate from your own.
Add the square footage of multiple rooms
Use Add another room or area for a separately measured space. Name it, calculate its net area, then add the results together. A living room floor of 120 sq ft and a kitchen floor of 80 sq ft total 200 sq ft.
A section changes the result for its room or area. Another room or area gets its own result in the list.
Formulas for other supported shapes
| Shape or layout | Area calculation |
|---|---|
| Triangle | Base × perpendicular height ÷ 2 |
| Round area | π × (diameter ÷ 2)² |
| Wider at one end | (First parallel end + second parallel end) × distance between ends ÷ 2 |
| Wall with a sloped top | Width × (left height + right height) ÷ 2 |
| Border around a rectangle | (Inside length + 2 × border width) × (inside width + 2 × border width) − inside length × inside width |
| Border around a circle | π × [(inside diameter ÷ 2 + border width)² − (inside diameter ÷ 2)²] |
Border calculations assume the same border width all the way around. A sloped-top wall assumes one straight sloping top.
Measure a triangular section
Measure the base, then the height at a right angle to that base. Use the perpendicular height, rather than the sloping edge. A 6 ft base and 4 ft height give 6 × 4 ÷ 2 = 12 sq ft.
Common room sizes in square feet
Both dimensions below are in feet. These examples describe rectangles; names such as bedroom or kitchen do not change the formula.
| Length × width | Area |
|---|---|
| 10 ft × 10 ft | 100 sq ft |
| 10 ft × 12 ft | 120 sq ft |
| 12 ft × 12 ft | 144 sq ft |
| 12 ft × 15 ft | 180 sq ft |
| 15 ft × 20 ft | 300 sq ft |
Estimate flooring materials and cost
First calculate the area you want to cover. Then, if needed, open Estimate materials & cost next to your result. Select the measured areas that use the same material, enter a waste allowance, and use the product's coverage and price.
Example: 120 sq ft, a chosen 10% waste allowance, and 20 sq ft per box
- Measured net area
- 120 sq ft
- Required including waste
- 132 sq ft
- Whole boxes to buy
- 7 boxes
- Purchased coverage
- 140 sq ft
At an example price of $5 per sq ft, 140 sq ft × $5 = $700 in material cost.
The waste percentage here is an example, not a rule for every material. Check product instructions and packaging. The estimate excludes tax, delivery, installation and cutting-layout planning.
Estimate materials for your measured areasConvert square feet to other area units
Use these relationships when you already know the area. Converting an area is different from converting a length.
| From square feet to | Calculation |
|---|---|
| Square meters (m²) | sq ft × 0.09290304 |
| Square yards (sq yd) | sq ft ÷ 9 |
| Acres | sq ft ÷ 43,560 |
| Square inches (sq in) | sq ft × 144 |
For example, 120 sq ft is approximately 11.15 m² or 13.33 sq yd. In the calculator, choose m, cm or mm for metric length input; area and material coverage are shown in m².
Convert square feet and square meters →
Understand square feet and area conversions →
Unit definitions: NIST Guide to the SI. Conversions use the international foot.
Square footage questions
What is the difference between feet and square feet?
Feet measure length. Square feet measure area. A 12-foot edge gives only one dimension; you also need a width or another dimension required by the selected shape to calculate area.
Should I include closets, furniture or built-in units?
Choose the surface you actually need to measure. Include a closet if its floor is part of your project. Furniture is not automatically a deduction. For walls, subtract only the openings or surfaces excluded from your intended coverage.
Why does the result say known subtotal?
At least one room or area still needs valid measurements. A known subtotal includes only completed areas. Finish the others before treating it as a complete total; the material panel also lets you deliberately select only measured areas.
Is adding room areas the same as measuring a home's official square footage?
The calculator totals the areas you enter. It does not determine property boundaries or which spaces qualify for a real estate listing or appraisal.
Does the material estimate include labor?
No. It uses the material price you enter and, when provided, whole-box quantities. Tax, delivery, preparation and installation are not included.
Content updated October 17, 2026.