What is a square foot?

A square foot is a unit of area equal to a square measuring 1 foot on each side (1 ft × 1 ft = 1 sq ft). It is the standard unit of area used in the United States to measure floor space, land area, and material coverage.

How do I calculate square feet?

Multiply the length of a space by its width, both measured in feet. For example, a room that is 10 feet long by 12 feet wide is 120 square feet (10 × 12 = 120 sq ft). For irregular shapes, divide the space into rectangles, calculate each area, then add them together.

How many square feet is a 12×12 room?

A 12×12 room is 144 square feet (12 × 12 = 144). This is a common size for secondary bedrooms, home offices, and dining areas. See our 12×12 room page for furniture and flooring estimates.

How do I convert square meters to square feet?

Multiply square meters by 10.7639 to get square feet. For example, 20 square meters equals about 215.3 square feet (20 × 10.7639 ≈ 215.28).

Do I subtract doors and windows when calculating square footage?

For flooring projects, you typically do not subtract doors and windows because flooring continues beneath thresholds. For paint or wallpaper, subtracting large windows and doors gives a more accurate material estimate.

What is the formula for square footage?

Length × Width = Area in square feet, when both length and width are in feet. For irregular spaces, divide into rectangles, calculate each rectangle, then sum the results.

How do US homes define square footage?

In the United States, residential square footage usually refers to Gross Living Area (GLA) as defined by the ANSI Z765 standard — finished, heated space measured at the exterior wall surfaces. Garages, unfinished basements, and open porches are excluded.

What is the average US home size?

The median new single-family home in the United States is about 2,200 square feet, with the average closer to 2,400 sq ft, based on National Association of Home Builders (NAHB) data.

Free Online Area Calculator

Free Square Feet Calculator

Calculate the square footage of any room, floor, wall, or land area in seconds. Works in feet or meters, supports waste allowance for material estimates, and requires no sign-up — accurate measurements you can take to the hardware store.

Imperial & metric units
Built-in waste allowance for flooring & tile
Free, no sign-up, no app to install

Length

Width

Unit of Measurement

Why Use Our Square Feet Calculator?

An accurate square feet calculatorsaves homeowners, contractors, and real-estate professionals from two expensive mistakes: buying too little material and running out mid-job, or buying too much and wasting money. Whether you're estimating flooring,paint, tile, or carpet, the right square footage is the foundation of every quote and shopping list.

This calculator handles both imperial (feet, inches) and metric (meters) input, converts between units automatically, and adds an optional waste percentage that mirrors the recommendations from the National Wood Flooring Association and major retailers like The Home Depot.

Pick the Calculator for Your Project

Different jobs need different math — flooring needs waste allowance, paint needs coverage rates, roofing needs a pitch multiplier. Use the calculator that matches your project.

Room Square Footage Calculator

Measure room dimensions and get instant area for floors, paint, and HVAC.

Flooring Calculator

Estimate flooring material needed with industry-standard waste percentages.

Paint Coverage Calculator

Calculate how many gallons of paint you need based on wall area and coats.

Tile Calculator

Compute total tiles, boxes, and waste for floor or wall tile projects.

Carpet Calculator

Calculate carpet square footage and yards including seam and pile allowance.

Wallpaper Calculator

Calculate wall area and the number of wallpaper rolls needed for a room.

How to Calculate Square Feet (Step by Step)

Measure the length of your space in feet using a 25-foot tape measure with a locking mechanism. Take the measurement at floor level where the wall meets the floor.
Measure the width on the perpendicular wall in feet. Keep the tape straight and taut so the measurement is not inflated by sag.
Multiply length × width to get the area in square feet — a 10 ft by 12 ft room is 120 sq ft. For metric input, the calculator converts automatically.
For irregular shapes,break the space into rectangles, calculate each rectangle's area, then add them together. L-shaped rooms are two rectangles; round features can usually be approximated with the largest rectangle that fits inside plus a half-circle.
Add a waste allowance when ordering materials — 5–10% for straight-lay flooring and tile, up to 15% for diagonal or herringbone patterns.

Standard Room Sizes (NAHB Reference)

Typical dimensions for new single-family homes in the United States, based on figures published by the National Association of Home Builders. Use these as a sanity check for your own measurements.

Room Type	Small	Average	Large
Master Bedroom	12'×14' (168 sq ft)	14'×16' (224 sq ft)	16'×20' (320 sq ft)
Secondary Bedroom	10'×10' (100 sq ft)	11'×12' (132 sq ft)	12'×14' (168 sq ft)
Living Room	12'×16' (192 sq ft)	16'×20' (320 sq ft)	18'×24' (432 sq ft)
Dining Room	10'×12' (120 sq ft)	12'×14' (168 sq ft)	14'×18' (252 sq ft)
Kitchen	8'×10' (80 sq ft)	10'×12' (120 sq ft)	12'×16' (192 sq ft)
Full Bathroom	5'×8' (40 sq ft)	7'×10' (70 sq ft)	10'×14' (140 sq ft)
Half Bathroom (Powder)	3'×6' (18 sq ft)	4'×6' (24 sq ft)	5'×8' (40 sq ft)
Home Office	8'×10' (80 sq ft)	10'×12' (120 sq ft)	12'×14' (168 sq ft)
Laundry Room	6'×7' (42 sq ft)	8'×10' (80 sq ft)	10'×12' (120 sq ft)
Walk-in Closet	4'×5' (20 sq ft)	6'×8' (48 sq ft)	8'×12' (96 sq ft)

Common Uses for a Square Feet Calculator

Home Improvement

Estimate flooring,paint, tile, and carpet quantities. Accurate measurements prevent the two most common mistakes: running out of material mid-job and over-ordering.

Real Estate

Square footage is the primary metric for listing price and home value. Most US listings report Gross Living Area calculated to the ANSI Z765 standard — finished space only, measured at the exterior wall.

Interior Design

Use room dimensionsto size furniture, rugs, and lighting correctly. Designers typically allocate 30–40% of a room's area to circulation space.

HVAC & Energy

Heating and cooling loads scale with floor area. A common rule of thumb is 20 BTU per square foot of cooling capacity for mild climates, with adjustments for insulation and ceiling height.

Frequently Asked Questions

Square Footage Guides & Tutorials

Deep-dive guides on measuring, converting, and estimating materials for every room of the house.

Sources

The figures on this page are based on data from these authoritative industry sources.

National Association of Home Builders (NAHB) — US home building industry data, including average new-home square footage.
ANSI Z765 Standard — American National Standard for measuring single-family residential square footage.
National Wood Flooring Association (NWFA) — Installation guidelines and waste recommendations for wood flooring.
Sherwin-Williams Technical Data — Paint coverage rates per gallon from the manufacturer’s product data sheets.