How to measure a room for square footage
Square footage is the starting number for almost every home project: flooring, carpet, sod, paint, tile, underlayment and even furniture layouts. Getting it right takes a tape measure, a notepad and about ten minutes.
- Measure wall to wall at floor level. Run the tape along the baseboard, not across the middle of the room where furniture gets in the way. If walls are not quite parallel, measure both ends and use the larger number.
- Round up to the nearest inch, then convert. Convert inches to decimal feet by dividing by 12 (7 in = 0.58 ft). A room that is 11 ft 7 in long is 11.58 ft.
- Sketch the floor plan. A rough drawing with every measurement written on it prevents most mistakes and is handy at the store.
- Include closets and doorways if the material continues into them. Flooring usually runs under the door to the threshold.
Breaking odd shapes into simple ones
Few rooms are perfect rectangles. The calculator above lets you add as many areas as you need, so split the space into rectangles, circles and triangles and add a row for each.
- L-shaped rooms: draw one line to cut the L into two rectangles. Measure each one separately.
- Bay windows or angled corners: treat the angled part as a triangle (base × height ÷ 2) or a small rectangle plus a triangle.
- Round patios or planting beds: measure straight across the widest point for the diameter. The calculator uses π × radius², where the radius is half the diameter.
Worked example
Say you have an L-shaped living area. The main section measures 14 ft × 12 ft, and a dining nook off one side measures 8 ft × 6 ft.
- Main section: 14 × 12 = 168 sq ft
- Nook: 8 × 6 = 48 sq ft
- Total: 168 + 48 = 216 sq ft, which is 216 ÷ 9 = 24 sq yd
Enter 10 in the waste box and the calculator returns about 237.6 sq ft. That is the number to shop with for a straight-lay floor.
How much extra to add
The waste box adds a percentage on top of the measured area to cover cuts, mistakes and pieces that do not fit. Common rules of thumb:
- Straight-lay laminate, vinyl plank or engineered wood: about 5–10%
- Diagonal or herringbone patterns: about 10–15% or more
- Carpet: depends on roll width and seam placement; let the installer measure
- Sod: about 5% for simple shapes, more for curvy beds
Leave the waste at 0 when you only want the true area, for example to compare against a real estate listing or calculate a price per square foot.
Common mistakes
- Mixing inches and feet. Entering 132 for an 11 ft wall gives an area twelve times too large.
- Measuring once. Check the long dimension twice. One wrong digit throws off the whole order.
- Forgetting the units conversion. Square yards are square feet ÷ 9, not ÷ 3. Square meters are square feet × 0.0929.
- Subtracting small obstacles. For flooring, do not subtract a kitchen island or closet unless it is large. The cuts around it use up the savings.
Buying tips
Flooring is sold by the box, and each box lists how many square feet it covers. Divide your total (with waste) by the box coverage and round up. Carpet and vinyl sheet are usually priced per square foot or square yard but cut from rolls of fixed widths, so seams can add material. Sod is sold by the piece, roll or pallet, and pallet coverage varies by farm, so ask the supplier. Buy flooring from one production lot when possible, and keep a spare box for future repairs.
Fast, accurate room measurements