Unit converter· 3 min read
Square Feet to Square Metres: Converting US Flooring and Paint Instructions
Square feet to m², gallons to litres and paint coverage in sq ft per gallon turned into m² per litre. A 12 × 15 ft room worked through step by step for DIY.
A flooring box from a US store says “covers 20 sq ft”, a paint can says “400 sq ft per gallon” and the plan shows a 12 × 15 ft room. To know how much to buy you need it in m² and litres. The conversions are exact and simple — you just need to know which number to multiply by.
Basic conversions
| Unit | Exactly |
|---|---|
| 1 sq ft (ft²) | 0.09290304 m² |
| 1 m² | 10.764 sq ft |
| 1 sq yd (yd²) | 0.83612736 m² |
| 1 US gallon | 3.785411784 l |
| 1 UK gallon | 4.54609 l |
A square foot is a square with 304.8 mm sides, so 0.3048 × 0.3048 = 0.09290304 m². The US gallon is exactly 231 cubic inches; the UK (imperial) gallon is larger — if the instructions come from Britain, use 4.546 l.
Example: a 12 × 15 ft room
- 1Area in feet: 12 × 15 = 180 sq ft.
- 2Conversion: 180 × 0.09290304 = 16.72 m².
- 3Check via the sides: 12 ft = 3.658 m, 15 ft = 4.572 m, 3.6576 × 4.572 = 16.72 m². Same result.
Once you know the area in sq ft, counting packs is easier in feet: a “20 sq ft” box covers 1.858 m² and 180 sq ft takes 180 / 20 = 9 boxes, with no allowance for cuts. Add the allowance the flooring maker recommends.
“10 sq ft per m²” is not good enough
Rounding 1 m² ≈ 10 sq ft gives 18 m² for the room instead of 16.72 m² — 7.6 % too much. The other way, rounding a foot to 0.3 m gives 3.6 × 4.5 = 16.2 m², and you buy too little. With areas, an error in length counts twice, so use the exact factor.
Paint coverage: sq ft per gallon → m² per litre
If the can states 400 sq ft per US gallon, convert in two steps:
- 1400 sq ft = 37.16 m².
- 21 US gallon = 3.785 l.
- 337.16 / 3.785 = 9.82 m² per litre for one coat.
A 30 m² wall with two coats then needs 2 × 30 / 9.82 ≈ 6.1 l. If the figure were per UK gallon, the coverage per litre would come out lower — so always check where the number comes from.
Unit converterOpen the converter with 180 sq ftLinear feet and cubic feet
US stores price trim, cladding and lumber by the “linear foot” — that is simply feet of length. Our room's perimeter is 2 × (12 + 15) = 54 ft, or 16.46 m of baseboard before you subtract the door. Mulch, soil and sand are sold in cubic feet: a “2 cu ft” bag holds 56.6 l, and one cubic foot is 28.3 l.
Workshop tips
- Convert the room's sides, not just the final area — when cutting the flooring you will need lengths in millimetres.
- US stores use sq yd for carpet: 20 sq yd = 16.72 m², the same as our room.
- Coverage on the can is the maker's figure for a smooth surface. Porous or rough surfaces may take more — follow the guidance for that product.