How Many Square Feet Is a 20x40 Room?
A 20 × 40 ft room is 800 square feet — 74.32 square metres, or 88.89 square yards.
Multiply the two sides together: 20 × 40 = 800. In metric that is 6.1 m × 12.19 m = 74.32 m².
| Unit | Area |
|---|---|
| sq ft | 800 |
| m² | 74.32 |
| sq yd | 88.89 |
| sq in | 115,200 |
| acres | 0.018365 |
What fits in a 20x40 room
Counted as a plain grid layout in whichever direction packs more in, with no walkways and no diagonal placement — so treat each figure as the floor, not the ceiling.
| Item | Footprint | How many fit | Floor used |
|---|---|---|---|
| King bed | 6.3 × 6.7 ft | 18 | 95% |
| Queen bed | 5 × 6.7 ft | 24 | 100% |
| Full (double) bed | 4.5 × 6.3 ft | 24 | 84% |
| Twin bed | 3.2 × 6.3 ft | 36 | 89% |
| Three-seat sofa | 3.2 × 7 ft | 30 | 83% |
| Dining table (seats 6) | 3 × 6 ft | 39 | 88% |
| Office desk | 2.5 × 5 ft | 64 | 100% |
| Parking space | 9 × 18 ft | 4 | 81% |
| Compact car | 6 × 15 ft | 6 | 68% |
| Ping-pong table | 5 × 9 ft | 16 | 90% |
| 8×10 area rug | 8 × 10 ft | 10 | 100% |
| Yoga mat | 2 × 5.7 ft | 70 | 99% |
How a 20 × 40 ft room lays out
At 2:1 this is a long, narrow footprint — 800 sq ft of floor, but only 20 ft across. Everything has to line up along the two long walls, and it is the width rather than the area that limits what will go in.
At 20 ft across, the width takes 2 standard 9 ft parking bays side by side, with 2 ft left over to open the doors. Split down the middle it gives two 10 × 40 ft bays, or four 10 × 20 ft quarters — useful if the space is going to be zoned rather than used as one room.
A footprint this size and shape is typically a workshop or small shop floor — typical ranges rather than a rule, and ballpark rather than sourced, like the figures above (see the methodology page).
Materials for 800 square feet
Quantities include each material's usual waste allowance and round up to whole units, because you cannot buy part of a box.
| Material | Sq ft to buy | Quantity |
|---|---|---|
| Carpet | 880 (+10%) | 74 roll feet |
| Drywall | 880 (+10%) | 28 sheets |
| Flooring (laminate/vinyl) | 880 (+10%) | 45 boxes |
| Hardwood Flooring | 880 (+10%) | 41 boxes |
| Paint | 840 (+5%) | 3 gallons |
| Tile | 880 (+10%) | 59 boxes |
Working with a 20x40 room
A 20 by 40 foot room is 800 square feet of floor, which is 74.32 square metres, 88.89 square yards, or 0.0184 of an acre. The arithmetic is a single multiplication — 20 × 40 — and every other figure on this page follows from it.
The walls are a different number. The perimeter of a 20 × 40 room is 120 feet, so with a standard 8 ft ceiling the four walls come to about 960 square feet before you deduct anything. Take off roughly 21 square feet for each door and 15 for each window: one door and two windows brings it to about 909 square feet, which at 375 square feet to the gallon is 3 gallons of paint per coat, or 6 for the two coats a colour change needs.
For flooring or tile, add the waste factor before you order rather than after. At the usual 10% allowance a 800 square foot floor needs 881 square feet of material bought, and a diagonal or herringbone lay pushes that to 920. The table above rounds each material up to whole boxes and sheets, because that is the smallest unit anyone will sell you.
If your room is not quite these dimensions, the calculator below gives the exact figure — or pick a shape from the calculator index if the room is not a plain rectangle. To add this room into a whole-house figure, use the multi-room calculator.
Measuring a different room
Change the numbers below and the live preview redraws this room to scale — or drag the drawing's handles to resize it. Switch to the drawing grid to sketch a room that is not a plain rectangle.
Live scale preview
The shape is drawn to scale and relabelled as you type.
An example to start from. Drag a handle or type a measurement and it becomes yours.
Frequently asked questions
How many square feet is a 20x40 room?
A 20 by 40 foot room is 800 square feet. Multiply the two sides together — 20 × 40 — and that is the floor area. The same figure is shown above in square metres, square yards and acres, along with a to-scale drawing and the quantity of each material a room this size needs.
What can fit in a room this size?
The table above counts how many of each item fit as a plain grid, laid whichever way round packs more in, with no walkways and no diagonal placement. Treat every figure as a floor rather than a ceiling: it tells you the room is physically large enough, not that the layout would be comfortable. A usable room generally needs 30 to 36 inches of clearance on at least one side of each piece of furniture.
Is this the floor area or the wall area?
The floor area. Wall area is a different calculation: multiply each wall's width by the ceiling height and add them together, then subtract the doors and windows. For a 20 by 40 room with an 8 ft ceiling, the four walls come to about (20 + 40) × 2 × 8 square feet before any deductions.