Square Footage Calculator

Knowing the exact square footage of a space is the starting point for nearly every home improvement, real estate, and construction decision.

Reviewed by: CalcMojo Editorial Team

Whether you are pricing flooring materials, estimating paint coverage, listing a property, or planning a landscaping project, accurate area measurements prevent costly overbuys and frustrating shortages. This square footage calculator lets you compute the area of any space in seconds by entering basic dimensions.

The tool handles rectangular, triangular, and circular areas, which together cover the vast majority of real-world measurement scenarios. Enter your dimensions in feet, inches, meters, or centimeters, and the calculator converts everything to square feet automatically. It also displays results in square meters and acres for users who need those units for international projects or land measurements.

Beyond single rooms, you can add multiple areas together to get a total for an entire floor plan, a multi-section yard, or a building footprint with irregular dimensions. The calculator also supports subtraction for cutouts like closets, stairwells, or areas you want excluded from the total. Use this tool before visiting the hardware store, meeting with a contractor, or listing a property, and you will have the precise numbers you need to move forward with confidence.

How to Calculate Square Footage

Square footage is the area of a space expressed in square feet. For a simple rectangle, the formula is straightforward:

Area = Length x Width

A room that measures 12 feet long and 10 feet wide has an area of 120 square feet. If your measurements are in feet and inches, convert the inches to a decimal first. For example, 12 feet 6 inches becomes 12.5 feet (since 6 inches is 0.5 feet). Then multiply normally: 12.5 x 10 = 125 square feet.

For triangular areas, the formula is:

Area = (Base x Height) / 2

A triangular section with a 10-foot base and an 8-foot height has an area of 40 square feet.

For circular areas, the formula uses the radius:

Area = pi x r^2

A circular patio with a 6-foot radius has an area of approximately 113.1 square feet.

Most real-world spaces are not perfect rectangles. An L-shaped room, for instance, can be divided into two rectangles, each calculated separately, with the results added together. This calculator handles that process for you by letting you add multiple sections and combine them into a single total.

Square Footage for Common Home Projects

Different projects require square footage calculations for different reasons. Here is how the measurement applies to the most common scenarios.

Flooring. When purchasing hardwood, laminate, tile, or carpet, you need the total floor area to determine how many boxes, rolls, or cases to buy. Material is sold by the square foot, and most installers recommend adding 10% for waste on standard rectangular rooms and 15% for diagonal installations or rooms with many cuts. Use our Flooring Calculator to get a materials estimate once you have your square footage.

Paint. Paint coverage is measured in square feet per gallon. A gallon of standard interior paint typically covers 350 to 400 square feet. For walls, you need the wall area rather than the floor area. Multiply the perimeter of the room by the ceiling height, then subtract the area of doors and windows. Our Paint Calculator handles this calculation directly.

Landscaping. Mulch, gravel, sod, and seed are all priced and measured by coverage area. Measure the length and width of each garden bed or lawn section, calculate the square footage, and you can determine exactly how many cubic yards of material you need. The Mulch & Gravel Calculator takes your square footage and depth to produce a volume estimate.

Real Estate. Square footage is one of the primary metrics in property valuation. Lenders, appraisers, and buyers all rely on accurate square footage when setting or evaluating a price. Gross living area (GLA) typically includes all finished, heated living space measured from the exterior walls. Garages, unfinished basements, and covered porches are usually excluded from GLA but may be noted separately.

Concrete. Patios, driveways, sidewalks, and foundations all start with a square footage measurement. Once you know the area, multiply by the slab thickness to get the volume, which determines how many cubic yards of concrete to order. Our Concrete Calculator walks you through that process.

Converting Square Footage to Other Units

Square footage is the standard in the United States, but other units are used internationally or for specific applications.

• 1 square foot = 0.0929 square meters. Multiply square feet by 0.0929 to convert to square meters.
• 1 square meter = 10.764 square feet. Multiply square meters by 10.764 to convert to square feet.
• 1 acre = 43,560 square feet. Divide square feet by 43,560 to convert to acres.
• 1 square yard = 9 square feet. Divide square feet by 9 to convert to square yards, which is common for carpet pricing.

This calculator displays all relevant conversions automatically so you do not need to perform these calculations manually.

How to Measure a Room Accurately

Accurate measurements start with good technique. Here are the steps professionals follow.

Use the right tool. A 25-foot tape measure works for most rooms. For larger spaces, a laser distance measure is faster and more accurate over long distances. Laser measures are accurate to within 1/16 inch and eliminate the sagging and bending issues that occur with long tape pulls.

Measure wall to wall. Place one end of the tape flush against one wall and extend it to the opposite wall. Measure at the floor level, not at waist height, since walls are not always perfectly plumb. Record the measurement in feet and inches.

Break complex shapes into rectangles. An L-shaped room is two rectangles. A room with a bay window can be measured as a main rectangle plus the bay area. Sketch the floor plan on paper, label each section with its dimensions, calculate each section separately, and add the results.

Account for fixed obstacles. Built-in cabinets, fireplaces, and closets may or may not be included in your measurement depending on the purpose. For flooring, exclude areas that will not be covered. For real estate listings, follow your local measurement standards, which typically include closets but exclude garages.

Measure twice. This is not just a cliche. Errors in measurement translate directly into wasted materials and money. Take each measurement at least twice and use the average if the numbers differ slightly.

Square Footage in Real Estate: What Counts

How square footage is measured for real estate purposes varies by state and local convention, but several general rules apply across the US.

Included in gross living area (GLA): All finished, heated, above-grade living spaces. This covers bedrooms, living rooms, kitchens, bathrooms, hallways, and closets. Finished attic space with adequate ceiling height (typically 7 feet or more) is usually included if it is heated and accessible by a permanent staircase.

Excluded from GLA: Garages, unfinished basements, unfinished attics, screened porches, and covered patios. These may be noted separately in listings and appraisals but are not counted in the primary square footage figure.

Below-grade space. Finished basements are a gray area. In many markets, below-grade finished space is listed separately because its value per square foot is lower than above-grade space. An appraiser might note 2,400 square feet above grade and 800 square feet finished below grade, rather than calling the home 3,200 square feet.

Measurement standard. The American National Standards Institute (ANSI) published the ANSI Z765 standard for measuring single-family homes. While not legally required in all states, it is widely used by appraisers and real estate professionals. Under ANSI Z765, measurements are taken from the exterior of the building, not the interior, which is why builder-provided square footage sometimes differs from what you measure inside.

If you are buying or selling a home and the square footage seems inconsistent, verify the measurement method. A home measured from exterior walls will have a higher figure than one measured from interior walls due to wall thickness.

Common Square Footage Mistakes

Forgetting to convert inches to decimal feet. A room that is 15 feet 8 inches long is 15.67 feet, not 15.8 feet. Eight inches divided by 12 equals 0.67.

Measuring only the main area. Closets, nooks, and alcoves add up. A 4 x 6 foot closet adds 24 square feet, and most homes have several of them.

Not accounting for waste. Raw square footage tells you the area, but material purchases need a waste factor. Tile, hardwood, and laminate all require extra material for cuts, breakage, and pattern matching.

Confusing square feet with linear feet. Baseboards and crown molding are sold by the linear foot (the perimeter of the room), not the square foot (the area). The perimeter of a 12 x 10 room is 44 linear feet, while the area is 120 square feet.

Using builder specs without verifying. Builder-quoted square footage is measured from exterior walls and includes wall thickness. Your actual usable interior space is smaller. If you are buying materials for the interior, measure interior dimensions yourself.

These estimates are approximate and based on standard material calculations. Actual quantities and costs vary by region, supplier, material grade, and site conditions.

Frequently Asked Questions

How do I calculate the square footage of a room?

Measure the length and width of the room in feet, then multiply the two numbers together. For example, a room that is 14 feet long and 12 feet wide has a square footage of 168 square feet. If the room is not a simple rectangle, divide it into rectangular sections, calculate each section separately, and add the results together.

How many square feet is a 12×12 room?

A 12 x 12 room is exactly 144 square feet. This is equivalent to 16 square yards or approximately 13.4 square meters. It is a common bedroom size and typically requires about 160 square feet of flooring material when you account for a 10% waste factor.

How do I convert square feet to square meters?

Multiply the square footage by 0.0929 to get square meters. For example, 200 square feet equals approximately 18.58 square meters. To convert in the other direction, multiply square meters by 10.764 to get square feet.

How do I calculate square footage for an irregularly shaped room?

Break the room into simple shapes like rectangles, triangles, or semicircles. Calculate the area of each section using the appropriate formula and add them together. For an L-shaped room, divide it into two rectangles. This calculator lets you add multiple sections together for exactly this purpose.

What is the difference between square feet and linear feet?

Square feet measure area (length times width), while linear feet measure only length in one direction. You use square feet for flooring, paint coverage, and property size. You use linear feet for baseboards, fencing, and countertop edges. A 10 x 12 room has 120 square feet of area but 44 linear feet of perimeter.

How much extra material should I buy beyond the exact square footage?

For most flooring projects, add 10% to account for cuts, waste, and future repairs. For diagonal installations or rooms with many angles, add 15%. For tile, the waste factor depends on the tile size and layout pattern; larger tiles in small rooms produce more waste. Always round up to the next full box or case.

Does square footage include closets?

For real estate listings and appraisals, yes. Closets, hallways, and other enclosed living spaces are included in the gross living area. For flooring projects, include closet area only if you plan to install flooring there. This calculator lets you add or subtract sections so you can include or exclude closets as needed.

How do I measure square footage for an apartment?

Measure each room individually by multiplying its length by its width, then add all the room areas together. Include hallways, closets, and bathrooms. Exclude any shared spaces like building lobbies or common areas. If the apartment has unusual shapes, break each room into rectangular sections before measuring.

Sources & Methodology

• Area calculations use standard geometric formulas for rectangles, triangles, and circles.
• Waste factor recommendations (10%-15%) based on National Association of Home Builders (NAHB) installation guidelines.
• Real estate measurement standards reference ANSI Z765-2021, the American National Standard for measuring single-family residences.
• Unit conversions based on the International System of Units (SI) and US customary measurement standards.

Default values shown are illustrative. Always verify measurements on site. Data accurate as of: March 2026