📐 Square Footage Calculator: Find the Area of a Room in Sq Ft
By ToolNimba Editorial Team · Updated 2026-06-20
Add the length and width of each room. Areas are added together for the total.
This square footage calculator finds the area of a room or surface from its length and width. Enter the two measurements in feet or switch to meters, and you will instantly see the area in both square feet and square meters. You can add as many rooms as you like to get a running total, and enter a price per square foot to estimate the cost of flooring, paint, tile, or other materials.
What is the Square Footage Calculator?
Square footage is simply the area of a flat surface measured in square feet. For any rectangle, area equals length multiplied by width, so a room that is 12 feet long and 10 feet wide is 12 x 10 = 120 square feet. The same rule works in any unit: multiply the two sides measured in the same unit and the result is in that unit squared. The only catch is that both measurements must use the same unit before you multiply, which is why this tool converts meters to feet behind the scenes when you switch units.
Most real spaces are not a single clean rectangle. A typical floor plan is an L shape, has an alcove, or combines several rooms. The standard approach is to break the space into rectangles, work out the area of each one, and add them together. That is exactly what the "add room" feature does: each row is one rectangle, and the calculator sums them into a grand total. For a space with a cut-out (such as a kitchen island footprint you do not want to floor), calculate the full rectangle and subtract the cut-out area separately. Other shapes have their own formulas: a circle is pi times the radius squared, a right triangle is half of base times height, and a trapezoid is the average of the two parallel sides times the height.
Knowing the total square footage is the first step to estimating materials and cost. Flooring, tile, carpet, and turf are usually priced per square foot or per square meter, so multiplying your area by the unit price gives a quick budget. Professionals then add a waste allowance (commonly 5% to 15%) for cuts, breakage, and pattern matching, so it is wise to order a bit more than the bare area suggests. This calculator gives you the exact area; add your own waste margin on top before buying.
When people ask for the square footage of a whole house, the number on a real estate listing usually means the Gross Living Area, or GLA. Under the widely used ANSI Z765 standard, GLA counts only the finished, heated, above-grade living space that is directly accessible from the main body of the home. Appraisers measure from the outside of the exterior walls, sketch each floor separately, and round each dimension to the nearest 0.5 foot. To measure an existing home, walk each room, record length and width, and add a room row here for every rectangular section, just as you would for flooring.
Not every part of a home counts toward that headline figure. Garages, open porches, patios, balconies, and unfinished attics or basements are excluded from GLA. Finished basements are reported and valued separately because they sit below grade, even when they are fully finished walk-outs. Stairwells are typically counted once on the floor they descend from, and open two-story spaces are counted only on the floor with the actual surface. Because the rules vary by region and by appraiser, an official measurement for selling or financing should follow the local standard rather than a do-it-yourself estimate.
For measuring, a laser distance meter is faster and more accurate than a tape and is what most agents and appraisers use. Measure wall to wall at floor level, keep a simple sketch so you do not double-count, and decide up front whether you are measuring finished interior space, the footprint for flooring, or a wall surface for paint. The math is the same in every case; what changes is which areas you choose to include.
When to use it
- Working out how much flooring, carpet, or tile to buy for a room before a trip to the store.
- Estimating the cost of a project by multiplying the total area by a price per square foot.
- Adding several rooms together to find the total floor area of an apartment or house.
- Measuring a home for a real estate listing and separating finished living area from garage or basement space.
- Converting a room measured in meters into square feet for a US listing or supplier quote.
- Sizing paint, drywall, or wallpaper by calculating wall surface area instead of floor area.
How to use the Square Footage Calculator
- Choose your measurement unit: feet or meters.
- Enter the length and width of the first room or rectangular section.
- Click "Add room" to include more rectangles, and the areas are totalled for you.
- For an L-shape or alcove, split the space into rectangles and add one row per rectangle.
- Optionally enter a price per square foot to see an estimated cost.
- Read off the total in square feet and square meters at the bottom.
Formula & method
Worked examples
A single rectangular room measured in feet: 12 ft long by 10 ft wide.
- area = length x width
- area = 12 x 10 = 120 square feet
- in square meters: 120 x 0.09290304 = 11.15 m2
Result: 120 sq ft (about 11.15 m2)
An L-shaped room split into two rectangles: a 15 ft by 10 ft main area plus a 6 ft by 4 ft alcove.
- Rectangle 1 = 15 x 10 = 150 sq ft
- Rectangle 2 = 6 x 4 = 24 sq ft
- total area = 150 + 24 = 174 sq ft
Result: 174 sq ft total for the L-shaped room
Two rooms added together, then a flooring cost at $4.50 per sq ft with a 10% waste allowance.
- Room A = 12 x 10 = 120 sq ft
- Room B = 8 x 6 = 48 sq ft
- total = 120 + 48 = 168 sq ft
- with 10% waste: 168 x 1.10 = 184.8 sq ft to buy
- cost = 184.8 x $4.50 = $831.60
Result: About 185 sq ft to order, estimated cost $831.60
A room measured in meters: 5 m by 4 m, converted to square feet.
- area in m2 = 5 x 4 = 20 m2
- convert: 20 x 10.7639 = 215.28 sq ft
- (or convert sides first: 5 m = 16.404 ft, 4 m = 13.123 ft, then 16.404 x 13.123 = 215.28 sq ft)
Result: 20 m2 (about 215.28 sq ft)
Common area unit conversions
| From | To | Multiply by |
|---|---|---|
| Square feet (ft2) | Square meters (m2) | 0.09290304 |
| Square meters (m2) | Square feet (ft2) | 10.7639 |
| Square yards (yd2) | Square feet (ft2) | 9 |
| Square feet (ft2) | Square inches (in2) | 144 |
| Acres | Square feet (ft2) | 43,560 |
| Hectares | Square feet (ft2) | 107,639 |
Area formulas for common shapes
| Shape | Formula | Notes |
|---|---|---|
| Rectangle or square | length x width | The default for most rooms. |
| Right triangle | 0.5 x base x height | Useful for angled corners and gables. |
| Circle | pi x radius squared | Radius is half the diameter. |
| Trapezoid | 0.5 x (side A + side B) x height | For tapered rooms with two parallel walls. |
| L-shape | split into rectangles, then add | Use one room row per rectangle here. |
What counts toward house square footage (Gross Living Area, ANSI Z765)
| Space | Counts as GLA? |
|---|---|
| Finished, heated bedrooms and living rooms | Yes |
| Finished hallways and finished stairs | Yes, counted once |
| Garage (attached or detached) | No |
| Unfinished attic or basement | No |
| Finished basement (below grade) | Reported and valued separately |
| Open porch, patio, or balcony | No |
Suggested material waste allowance to add on top of the bare area
| Material | Typical waste to add |
|---|---|
| Laminate or vinyl plank | 5% to 10% |
| Carpet | 5% to 10% |
| Straight-lay tile | 10% |
| Diagonal or patterned tile | 15% |
| Hardwood | 5% to 10% |
Common mistakes to avoid
- Mixing units before multiplying. Length in feet and width in inches will not give square feet. Convert both measurements to the same unit first, then multiply. This tool keeps both sides in one unit for you.
- Forgetting to add a waste allowance. The calculated area is the exact surface. Cuts, breakage, and pattern matching mean you should buy 5% to 15% extra, so order a little more than the bare square footage.
- Treating an L-shaped room as one rectangle. Irregular rooms need to be split into rectangles. Measure each section, add a room row for each one, and the calculator totals them correctly.
- Counting garage, basement, or unfinished space as living area. For a house listing, Gross Living Area excludes garages, open porches, and unfinished space, and reports finished basements separately. Mixing these in inflates the square footage.
- Confusing square feet with linear feet. Square footage measures area (length x width). Linear feet measure a single length only, such as baseboard trim. They are not interchangeable.
- Measuring to the inside of trim instead of wall to wall. Measure the full wall-to-wall dimension at floor level. Stopping at the baseboard or furniture understates the room and leaves you short on materials.
Glossary
- Square foot (ft2)
- A unit of area equal to a square that is one foot on each side. It is the standard area unit for rooms and flooring in the US.
- Square meter (m2)
- The metric unit of area, equal to a square one meter on each side. One square meter is about 10.76 square feet.
- Area
- The size of a flat surface, found for a rectangle by multiplying its length by its width.
- Gross Living Area (GLA)
- The total finished, heated, above-grade living space of a home, the figure usually quoted as a house square footage on listings.
- Above grade
- Any level of a home that sits at or above ground level. Above-grade finished space counts toward GLA.
- Below grade
- Space below ground level, such as a basement. Finished below-grade area is reported separately from GLA.
- Waste allowance
- Extra material ordered beyond the exact area to cover cuts, offcuts, breakage, and pattern matching, usually 5% to 15%.
- Linear foot
- A measurement of length only, one foot long, used for trim or molding. Not the same as a square foot.
Frequently asked questions
How do I calculate square footage?
Multiply the length by the width when both are measured in feet. For example, a 12 ft by 10 ft room is 12 x 10 = 120 square feet. This calculator does the multiplication and totals multiple rooms for you.
How do I calculate the square footage of a whole house?
Measure the length and width of each finished room, multiply to get each area, and add them together. Sketch each floor separately and include only finished, heated, above-grade living space if you want the figure used on listings (Gross Living Area). Add a room row here for every rectangle to get the total.
How do I find the square footage of a room in meters?
Switch the unit toggle to meters and enter the length and width in meters. The tool shows the area in both square meters and square feet, converting automatically (1 m2 = 10.7639 ft2).
How do I calculate the area of an irregular or L-shaped room?
Split the space into rectangles, measure each one, and add a room row for each rectangle. The calculator adds the areas together to give the total square footage. For circular or triangular sections, use pi x radius squared for a circle and 0.5 x base x height for a triangle.
Does a garage or basement count toward square footage?
No. Under the common ANSI Z765 standard, garages and unfinished space are excluded from Gross Living Area, and finished basements are reported and valued separately because they sit below grade. Only finished, heated, above-grade space counts as living area.
How much flooring should I buy for my square footage?
Take the total square footage and add a waste allowance, commonly 5% to 15% depending on the material and layout. Order that higher amount so you have enough for cuts and breakage. Diagonal or patterned tile usually needs the larger 15% margin.
How do I convert square feet to square meters?
Multiply the square feet by 0.09290304 to get square meters, or divide by 10.7639. For example, 120 sq ft x 0.09290304 = about 11.15 m2. This tool shows both at once.
How do I estimate the cost from square footage?
Multiply the total square footage by the price per square foot. Enter the price in the optional field and the calculator shows the estimated cost instantly, before any waste allowance. Add 5% to 15% to the area first if you want a buy-it-all figure.
How many square feet are in an acre?
One acre is 43,560 square feet. To convert square feet to acres, divide by 43,560. For example, a 10,000 sq ft lot is about 0.23 acres.
What is the most accurate way to measure square footage?
Use a laser distance meter rather than a tape, measure each room wall to wall at floor level, and keep a sketch so you do not double-count shared or open areas. For an official sale or appraisal, hire a professional who follows the local measuring standard such as ANSI Z765.