Example 1
- Length: 5 m
- Width: 4 m
Floor area: 20.0 m²
This is the most basic case and the natural starting point for tiles, panels, boards, or carpet planning.
Floor area calculator
Type length and width in the header unit. The calculator multiplies the sides, subtracts openings, and adds waste. A 5 by 4 m room is 20.0 m². The same room minus 2.6 m² and plus 8% waste is 18.79 m² to buy. At 45 per m² the estimate is 845.64.
This is a basic planning calculator for tiles, panels, boards, and other flooring materials. Depending on the form fields, it can estimate not only area, but also waste allowance and approximate material cost. Next: tile quantity, tile adhesive, linear meter of boards.
Results
Length, width, openings, and waste. Floor area shows up here.
How the results are calculated
Floor area counts square meters for planks, tiles, or boards. The formula is max(0, length times width minus openings) times (1 plus waste). If you type a price, cost is material area times price. Openings are a stair, a hearth, or a nook you skip in the order.
A 5 by 4 m living room with no deductions is 20.0 m², the number you later paste into tiles or floor paint. After 2.6 m² off and 8% for cuts you get 18.79 m². At 45 per m² the result is 845.64. A 2.2 by 1.8 m closet at 10% and 79 per m² is 4.356 m² and 344.12.
Type length and width in the header unit. Deduct openings, waste, and price only when you need them. Empty openings deduct nothing; empty waste leaves the clean area. A comma and a period are the same side, so 2.2 and 2,2 both run.
Tile count from this area lives on the tile calculator: 18 m² at 60×60 cm and 10% is 56 pieces. Adhesive follows the same meters. Boards for a 20 m² deck at 14 cm and 8% are 154.29 linear meters on the boards page.
Eight percent waste on 17.4 m² net (20 minus 2.6) adds 1.39 m², because you still cut at walls and door frames. Adhesive bags round up on their own page. Mixing meters with centimeters in one field breaks the scale: 400 cm is 4 m, not 400.
Type 5 and 4, click Calculate, and match 20.0 m². Then deduct 2.6 and set 8%: 18.79 m², the second card.
How to use this calculator
- Type length and width in the header unit, for example 5 and 4. Both sides in the same unit.
- Optionally deduct openings in m², for example 2.6 for a stair or a hearth.
- Add waste for cuts, usually 5-10%, and a price per m² if you want a cost sketch.
- Click Calculate. 5 by 4 m is 20.0 m². With 2.6 m² off and 8% you get 18.79 m².
- Tiles and adhesive use this area on their pages. This calculator stays floor area.
m² of a 5 by 4 m floor
Sides multiplied, openings subtracted, waste added. A 5 by 4 m room is 20.0 m². Minus 2.6 m² and plus 8% is 18.79 m² to buy.
- m²
- Floor area. 5 × 4 = 20.0. After subtracting 2.6 and adding 8% you buy 18.79 m², not 14 m of perimeter.
- waste
- The cutting percent field. 8% on net 17.4 m² (20 − 2.6) is 18.79 m². At 45 per m² the estimate is 845.64.
Example scenarios
Example 2
- Length: 5 m
- Width: 4 m
- Deduction: 2.6 m²
- Waste: 8%
Material area: 18.79 m²
This gives a more realistic purchase estimate than the gross area alone, because it includes both deductions and cutting waste.
Example 3
- Length: 5 m
- Width: 4 m
- Deduction: 2.6 m²
- Waste: 8%
- Price: 45 per m²
Material area: 18.79 m²
Estimated cost: 845.64
This is a practical buying scenario - area and cost shown together make it easier to compare flooring options.
Example 4
- 2.4 × 1.6 m
- +10% waste
- 79 per m²
4.22 m² · cost 333.70
How much floor area is a 2.4×1.6 m bathroom at 10% waste? 4.22 m², cost 333.70.
Example 5
- 3.8 × 3.2 m
- −0.9 m² island
- +8% waste
12.16 m²
How much floor area is a 3.8×3.2 m kitchen minus a 0.9 m² island? 12.16 m².
Example 6
- 6.5 × 4.2 m
- +7% waste
- 89 per m²
29.21 m² · cost 2599.78
How much laminate for a 6.5×4.2 m living room at 7% waste? 29.21 m², cost 2599.78.
Example 7
- 7.2 × 1.15 m
- +12% waste
9.27 m²
How much floor area is a 7.2×1.15 m hallway at 12% waste? 9.27 m².
Example 8
- 6 × 3.5 m
- +5% waste
- 45 per m²
22.05 m² · cost 992.25
How much floor area is a 6×3.5 m garage at 5% waste? 22.05 m², cost 992.25.
Related calculators
FAQ
How many m² is a 5 by 4 m room?
20.0 m². That is clean area, with no waste and no openings.
How much material at 5 by 4 m, 2.6 m² off, and 8% waste?
18.79 m². Net is 17.4 m² after the cut-out, then times 1.08.
What does 18.79 m² cost at 45 per m²?
845.64, as on the third card. Price multiplies material area, not the raw 20 m².
What waste should I add for a floor?
Usually 5-10% for a straight plank layout. Herringbone and a diagonal sit closer to 10-15%. Tiles have their own waste on the tile page.
How many 60×60 cm tiles for those 20 m²?
On the tile calculator: 20 / 0.36 ≈ 55.56, plus 10% is 62 pieces. Here you keep 20.0 m².
How many linear meters of boards for 20 m² at 14 cm and 8%?
154.29 linear meters on the boards page. Floor area only gives square meters.
Can I type 400 cm as 400?
The field is meters. 400 cm is 4. Typing 400 would be a 400 m side.
What about 2.2 by 1.8 m, 10%, and 79 per m²?
4.356 m² and a cost of 344.12. A small closet, the same formula.
Do empty openings deduct zero?
Empty openings deduct nothing. A typed zero also leaves the full area.
Where do I count adhesive for those 18.79 m²?
On tile adhesive. At 3.5 kg/m² and 10% that is about 72 kg, bags rounded up.
Knowledge sources
Volume and waste come from the sizes you type. Below are volume and NIST SI units.
Page updated in 2026.