Square Footage Calculator

How to Calculate Square Footage

For any rectangular space, square footage is length multiplied by width. A room that is 14 feet long and 11 feet wide contains 154 square feet. The formula is the same regardless of the unit of measure — you just need both dimensions in the same unit before multiplying. This calculator handles the unit conversion for you, so you can mix inputs freely.

Most real-world spaces are not perfectly rectangular, but almost all can be broken down into rectangles. An L-shaped room becomes two rectangles. A room with a bay window extension becomes the main rectangle plus a smaller rectangle for the bay. Even triangular spaces can be handled by calculating the enclosing rectangle and taking half of it. Sketch your space, mark the measurements, and add the component rectangles together.

For very large or irregular outdoor spaces — a lawn, a garden, a land plot — the same principle applies, though you may need multiple measurements across different sections. If you have a roughly circular area like a flower bed, the formula is π × radius² (about 3.14159 times the radius squared). Our calculator handles rectangular shapes; for circles and triangles, see our area calculator.

Unit Conversion Reference

Area unit conversions can be unintuitive because they involve squared units. One foot is 12 inches, but one square foot is 144 square inches (12 × 12). Keep that in mind when converting — you always square the linear conversion factor.

Material Estimates by Project Type

The most common reason people calculate square footage is to figure out how much material to buy. Here are the key figures for the most frequent home improvement applications:

The waste allowance is not optional padding — it accounts for cuts at walls and doorways, broken tiles, and the fact that flooring is sold in fixed-size boxes or rolls. Buying exactly the square footage you measured almost always leaves you short. Most home improvement retailers allow returns on unopened boxes, so it's financially safer to buy slightly more than you need.

Square Footage in Real Estate

In residential real estate, square footage is used to calculate price per square foot — one of the primary metrics for comparing similar properties in a market. According to the National Association of Realtors, median home prices and price-per-square-foot figures vary dramatically by region — from under $100/sq ft in parts of the rural Midwest to over $1,000/sq ft in prime urban markets.

A critical point for buyers: real estate square footage is not uniformly measured. Most agents report "gross living area" (GLA), which includes only heated, finished, above-grade space. Finished basements, garages, sunrooms, and covered porches are typically excluded — even if they are fully usable and add significant value. The American National Standards Institute (ANSI) Standard Z765 defines the measurement methodology that professional appraisers use, but listing agents are not required to follow it. When comparing homes or evaluating price-per-square-foot, verify whether you are comparing GLA-to-GLA or something else.

Frequently Asked Questions

How do I calculate the square footage of an L-shaped room?

Divide the L-shape into two rectangles, calculate each area separately (length × width), then add them. For example: a room with a 20×15 ft main section and a 10×8 ft alcove gives 300 + 80 = 380 sq ft. The key is breaking any irregular shape into rectangles you can measure cleanly. For rooms with angled walls or curves, it helps to sketch the space on graph paper first so you can see which rectangles to use. You can also measure the full bounding rectangle and subtract the missing corner — both approaches give the same result.

How many square feet is a typical room?

Room sizes vary considerably by region, housing age, and price point, but U.S. averages from the National Association of Home Builders give a useful benchmark: a small bedroom is typically 100–130 sq ft, a standard bedroom 130–160 sq ft, and a master bedroom 200–350 sq ft. Living rooms average 250–400 sq ft, kitchens 100–200 sq ft, and master bathrooms 75–120 sq ft. The median newly built U.S. single-family home was approximately 2,300 sq ft as of recent data — though that figure has trended down slightly from a peak near 2,500 sq ft around 2015 as builders shift toward smaller, more affordable homes.

What is the difference between square feet and square meters?

One square meter equals exactly 10.7639 square feet, because one meter equals 3.28084 feet and area is length squared. To convert square feet to square meters, divide by 10.764. To convert square meters to square feet, multiply by 10.764. A 1,000 sq ft apartment is 92.9 square meters; a 100 square meter apartment is 1,076 sq ft. This conversion matters when comparing real estate listings internationally, reading European furniture dimensions, or working with metric-based building materials.

How do I accurately measure a room for square footage?

Use a tape measure and record the room's length and width at their maximum points, measuring from wall to wall at the floor level. For accuracy, take two measurements in each direction — walls in older homes are often not perfectly parallel, and averaging the two readings gives a better result. Write down each measurement before moving on. For rooms with closets, measure and add the closet area separately if you want the full usable square footage. Laser distance measurers (available for under $30) can make this much faster and more accurate than a tape measure alone for larger spaces.

How much flooring or paint do I need for my room?

For flooring, calculate the floor area in square feet, then add 10% for standard cuts and waste — or 15% for diagonal or herringbone installations. So a 400 sq ft room needs 440–460 sq ft of material ordered. For paint, the rule of thumb is one gallon covers 350–400 sq ft per coat on smooth walls. For textured walls or a first coat over bare drywall, expect 300–350 sq ft per gallon. Multiply wall height by total wall length to get wall area, then subtract window and door openings (roughly 20 sq ft each for a standard door, 15 sq ft for a standard window). Always buy slightly more than your calculation suggests — dye lots vary between batches and you may need touch-ups later.

How is square footage measured in real estate listings?

Real estate square footage is not uniformly standardized in the U.S., which can cause significant confusion. Most residential listings measure the 'gross living area' (GLA) — the heated, finished, above-grade interior space. Basements (even finished), garages, unfinished attics, and enclosed porches are typically excluded from GLA even if they add usable space. Appraisers generally follow ANSI Standard Z765 when measuring residential properties, but not all agents and builders use the same methodology. If the exact square footage matters for your purchase decision — because you're comparing price-per-square-foot across listings — ask the seller's agent how the figure was calculated and whether it was professionally appraised.