How to measure square footage
Clear the floor of the main obstacles so you can stretch a tape from wall to wall. For a simple rectangular room, measure length and width in feet (or meters) and multiply. That product is the floor area.
Many homes are not one clean rectangle. Walk-in closets, L-shaped living rooms, and bay windows throw off a single measurement. Split the space into shapes you can measure: rectangles, triangles, or a circular area such as a round patio. Enter each piece in the Rooms mode, or switch to Triangle or Circle for those shapes, then add the results.
Measure to the inside of finished walls if you are estimating flooring. If a doorway opens into a hall you are not covering, do not include that hall. For outdoor slabs and decks, measure the usable surface, not the surrounding yard.
Common mistakes
- Mixing inches and feet in the same field (enter decimal feet, e.g. 12.5 for 12 ft 6 in, or switch to metric).
- Measuring only one wall of a room that is not square.
- Forgetting a closet or bump-out that still needs flooring.
- Using outside building dimensions when you need interior floor area.
Waste for flooring and finishes
Area alone is not always what you order. Sheet vinyl and carpet often need extra for seams and pattern match. Tile and hardwood commonly get 5–10% waste; diagonal layouts and busy patterns can need more. This calculator shows area only — add waste when you talk to the supplier.
If you are sizing a roof, square footage of the building footprint is only the starting point. Pitch multiplies the surface area. Use the Roofing Calculator for squares, bundles, and waste on a simple gable.
FAQ
How do I measure a room for square footage?
Measure the longest length and the widest width in feet (or meters). Multiply them for a rectangle. For odd shapes, split the floor into rectangles, triangles, or a circle and add the areas.
Should I use feet or meters?
Use whichever matches your tape measure. The calculator defaults to feet and inches, and you can switch to meters and centimeters. The choice is remembered for this browser session.
Does square footage include walls or just the floor?
This tool calculates floor (or plan) area from the dimensions you enter. It does not add wall surface or ceiling height. For paint or drywall you need separate wall measurements.
What is a roofing “square”?
In U.S. roofing, one square equals 100 square feet of roof surface. The square footage calculator can show that conversion as a note; use the roofing calculator when you also need pitch and waste.