Result
Result reflects the current submitted inputs.
- Risk A
- Reviewed 2026-05-26
- 2 sources
- Length and width are entered in feet.
- Quantity represents identical rectangles.
- Blank quantity is treated as 1.
- Intermediate values are not rounded.
Accuracy notes
- Risk level
- A
- Reviewed
- 2026-05-26
- Sources
- 2
- Primary result
- Area per item
Formula logic is kept in a pure calculator module with fixtures, source notes, and page-visible assumptions.
What the result means
The result is the floor or surface area in square feet. Use it to buy materials: divide the total project area by the coverage of one box of flooring or one gallon of paint to find how many you need. Always add a waste allowance (usually 5% to 10%, more for diagonal or patterned layouts) so you do not run short mid-job.
Use the result this way
- Start with Area per item, then use supporting outputs for context.
- Verify Length, Width, and Quantity before copying the result.
- Check the formula, example, and assumptions before reusing the answer.
User job
How to use this calculator
Use Square Footage Calculator when you need area per item, then use total area to check the context for unit checks, engineering notes, recipes, travel, shopping, and measurement cleanup.
Best for
- Converting compatible units
- Auditing the factor used for a repeated conversion
- Reviewing a default example before entering your own length and width.
Check before relying
- Make sure the source and target units measure the same kind of quantity.
- Length and width are entered in feet.
- Quantity represents identical rectangles.
- Source context: National Institute of Standards and Technology, reviewed 2026-06-16.
Next useful step
- Area CalculatorUse next when your task shifts from Square Footage Calculator to Area Calculator.
- Volume CalculatorUse next when your task shifts from Square Footage Calculator to Volume Calculator.
- Surface Area CalculatorUse next when your task shifts from Square Footage Calculator to Surface Area Calculator.
Formula
For a rectangle, square footage = length (ft) x width (ft). A room 12 ft by 10 ft is 12 x 10 = 120 square feet. For other shapes: a triangle is base x height / 2, a circle is 3.14159 x radius squared, and an irregular space can be split into rectangles and triangles whose areas are added together. Measure in feet to get square feet directly; if you measure in inches, divide each measurement by 12 first.
- Rectangle or square: length x width. Triangle: base x height / 2. Circle: 3.14159 x radius x radius. Trapezoid: (base1 + base2) / 2 x height. Split any complex room into these shapes and add the areas.
- Unit conversions: 1 square yard = 9 square feet, 1 acre = 43,560 square feet, and 1 square foot = 0.0929 square meters. To convert square feet to square meters, multiply by 0.0929; to go the other way, divide.
- For flooring, tile, or carpet, add 5% to 10% extra for cuts and waste, and up to 15% for diagonal or herringbone patterns. For paint, one gallon typically covers about 350 to 400 square feet per coat.
- Measure each room wall-to-wall and in feet. For irregular or L-shaped spaces, divide the floor into rectangles, measure and calculate each, then add them together for the total square footage.
- Gross (building) square footage and usable (living) square footage differ. Real-estate listings often quote gross area measured to the outside of exterior walls, while usable area excludes walls, closets, and shared space. Confirm which one a figure refers to before comparing.
Inputs
Enter the length and width of the space in feet. For a rectangular room, that is wall-to-wall in each direction. The calculator multiplies the two to return the area in square feet. If a room is L-shaped or irregular, break it into rectangles, calculate each one, and add the results. Convert inches to feet first (divide by 12) so the answer comes out in square feet rather than square inches.
Example
A bedroom measuring 12 ft by 14 ft has an area of 12 x 14 = 168 square feet. A 10 ft by 10 ft kitchen is 100 square feet. For an L-shaped living room, split it into a 15 ft by 12 ft rectangle (180 sq ft) and a 6 ft by 8 ft rectangle (48 sq ft) for a total of 228 square feet.
FAQ
How do you calculate the square footage of a room?
Measure the length and width of the room in feet and multiply them. A room 12 feet by 10 feet is 12 x 10 = 120 square feet. For L-shaped rooms, split the space into rectangles, calculate each, and add the results.
How many square feet is a 12x12 room?
A 12 foot by 12 foot room is 12 x 12 = 144 square feet. The same method works for any rectangle: just multiply the two side lengths measured in feet.
How do you convert square feet to square meters?
Multiply the square footage by 0.0929. For example, 500 square feet x 0.0929 = about 46.5 square meters. To convert square meters back to square feet, divide by 0.0929 (or multiply by 10.764).
How do you measure the square footage of an irregular room?
Divide the space into simple rectangles and triangles, measure and calculate the area of each one, then add them together. This works for L-shaped rooms, bay windows, and any layout that is not a single rectangle.
How much extra should I add for flooring waste?
Add 5% to 10% to your square footage for cuts and waste with standard layouts, and up to 15% for diagonal or patterned installations. Buying a little extra also gives you matching material for future repairs.
How many square feet are in an acre?
One acre is 43,560 square feet. So a half-acre lot is 21,780 square feet, and a quarter-acre lot is 10,890 square feet.
Sources
Last reviewed: 2026-05-26
- officialReviewed 2026-06-16Special Publication 811: Guide for the Use of the International System of Units (SI)National Institute of Standards and Technology. Authoritative unit definitions and conversion factors for area units including square feet, square meters, and acres.
- academicReviewed 2026-06-16Prealgebra 2e, Section 9.4: Use Properties of Rectangles, Triangles, and TrapezoidsOpenStax. Area formulas for rectangles, triangles, and trapezoids used to compute square footage of common and composite shapes.
Disclaimer
Area results are estimates based on the measurements you enter. For flooring, paint, or material purchases, add a waste allowance and confirm coverage figures on the product packaging. For real-estate or legal purposes, rely on a professional measurement or survey.