Understanding your result
The headline is the floor area, with the same figure in square yards and square metres beneath it. The stats split it into what was added and what was subtracted. The table lists every part with its own area, so if the total surprises you, the part that caused it is easy to find.
Each part is a rectangle: the main body of the room, the leg of an L, a closet, a bay, an alcove. Parts marked subtract are taken away: a hearth, an island set on the subfloor, a built-in cabinet. If you subtract more than you add, the total is set to zero and the note says so. Square yards are square feet divided by nine; square metres use the exact factor 0.09290304.
The area is the room as measured, with no waste added. Take it to the calculator for your material: the floor tile calculator, the plank and carpet calculators, or the general boxes and cartons calculator, which each add the waste for their layout. To find the right waste for an unusual room, the waste factor calculator; for the wall length the trim needs, the perimeter calculator.
How we calculate this
The method is the one every installer uses: break the room into rectangles that do not overlap, measure each, add them. Where two rectangles share a wall, measure one of them to the shared line and the other from it, so no strip is counted twice. The conversion factors are exact by definition; the guide to flooring units explains them. The guide to measuring odd rooms has diagrams for L-shapes, bays, angled walls and rooms with an island, and the complete method walks a whole room from tape measure to boxes.
The assumptions behind the numbers
| Assumption | Default | Where it comes from |
|---|---|---|
| Example room | 16 × 12 ft main area, 8 × 6 ft leg, 6 × 3 ft closet, 4 × 2 ft hearth subtracted | Chosen to show adding and subtracting parts |
| Parts | up to six rectangles | Enough for most rooms; split a complex plan into two runs |
| Conversion | 1 ft = 0.3048 m exactly | International yard and pound agreement (1959) |
| Waste | none | Added by each material calculator for its layout |
Assumptions last reviewed October 8, 2026.
The calculator adds rectangles; it does not read a plan or a photo. Curved walls and circular bays are approximated by rectangles of about the same area. It does not decide what to subtract for you: the rule is that only what the floor stops at comes out. And it treats each measurement as given; it cannot know that a wall is out of square, which is why measuring both ends of each wall matters.
Two worked examples
An L-shaped bedroom
A 12 × 10 ft main area and a 6 × 4 ft leg by the window.
- Part 1: 12 × 10 = 120 sq ft
- Part 2: 6 × 4 = 24 sq ft
- Floor area: 144 sq ft, 16 sq yd, 13.38 m²
Measuring the room as one 12 × 14 ft rectangle would have given 168 sq ft and an extra box. Measuring only the main area would have given 120 and a box short.
A living room with a closet and a hearth
A 16 × 12 ft main area, an 8 × 6 ft dining leg, a 6 × 3 ft closet, and a 4 × 2 ft raised hearth the floor stops at.
- Added: 192 + 48 + 18 = 258 sq ft
- Subtracted: 4 × 2 = 8 sq ft
- Floor area: 250 sq ft, 27.78 sq yd, 23.23 m²
The hearth comes out because the new floor stops at it; the sofa and the piano do not, because the floor runs under them. That 250 is the figure to take to the material calculator, which will add its own waste.
Where to find your inputs
Each rectangle. Measure wall to wall at floor level, at both ends of each wall, and use the larger figure.
Closets and bays. Each is its own part, measured from the line where it meets the main room.
Doorways. The floor usually runs to the middle of the threshold; add a strip the width of the door and half the wall thickness if it matters.
What to subtract. Only things the floor will stop at.
Common mistakes
- Forgetting closets. They are often a box on their own.
- Overlapping rectangles. Measure each part to the shared line, not past it.
- Subtracting furniture. The floor goes under it.
- Adding waste here and again later. Leave the area clean; the material calculator adds waste.
- Measuring one end of each wall. Rooms are rarely square. Use the larger figure.
- Rounding every measurement up to the foot. Round to the inch; rounding up six dimensions adds a lot.
Questions people ask
- How do I measure an L-shaped room for flooring?
- Split it into two rectangles at the inside corner, measure each at its longest and widest points, and add them. A 12 × 10 ft main area with a 6 × 4 ft leg is 120 + 24 = 144 sq ft, which is 16 sq yd or 13.4 m².
- Should I include closets in the floor area?
- Yes, if the floor goes into them, which it usually does. Add each closet as its own rectangle. A 6 × 3 ft closet is 18 sq ft, which is most of a box of tile or plank.
- What should I subtract from the floor area?
- Only what the new floor will not go under, such as a raised hearth, a kitchen island or cabinets set on the subfloor, a built-in. Do not subtract freestanding furniture, appliances or a bathtub alcove the floor runs under.
- Do I add waste to the floor area?
- Not here. The floor area is the room as measured. Each material calculator on this site adds the waste for its own layout, 10% for a straight layout, 15% diagonal, 20% herringbone, so adding it twice would over-order.
- How do I measure a room with an angled wall?
- Split the angled part into a rectangle and a right triangle; the triangle is half its length times its width. In this calculator, enter the triangle as a rectangle with half the width, which gives the same area.
- How accurate does the measurement need to be?
- To the nearest inch, or half an inch in a small room. Measure each dimension at both ends of the wall and use the larger figure, because walls are rarely parallel and the floor must reach the wider end.