How much joint compound a room takes
USG publishes the figure as two 4.5 gallon pails for every 1,000 square feet of board, which is nine gallons a thousand, or 0.009 gallons a square foot. The 12 by 10 foot room this page opens with is 439 square feet of board net of its door and window, so it takes 3.95 gallons — 4.35 with the 10% allowed for waste, which is one 4.5 gallon pail.
That one figure covers the whole job: the bed coat on the tape, the fill coat and the skim. It is not a figure per coat, and the page does not split it by finish level — see below.
Rooms by size
| Room | Board | Compound | Buys as |
|---|---|---|---|
| 10 × 10 ft | 387 ft² | 3.83 gal | 1 × 4.5 gal |
| 12 × 10 ft | 439 ft² | 4.35 gal | 1 × 4.5 gal |
| 12 × 12 ft | 495 ft² | 4.90 gal | 1 × 4.5 gal + 1 × 1 gal |
| 14 × 16 ft | 671 ft² | 6.64 gal | 2 × 3.5 gal |
| 20 × 24 ft | 1,151 ft² | 11.39 gal | 1 × 4.5 gal + 2 × 3.5 gal |
Walls and ceiling, 8 foot walls, one door and one window out of each, 10% for waste. The compound is worked out on the board area, so taking the openings out takes their mud out too. The combinations are the cheapest at the prices this page starts with, which is why a 4.9 gallon job buys a 4.5 and a 1 rather than two 4.5s — type your store's prices in and the mix moves.
Which container
All-purpose compound is sold ready-mixed in a 4.5 gallon pail (about 61 pounds), a 3.5 gallon box and a 1 gallon pail. The page works out all three and picks the cheapest combination at the prices beside them; type your store's in and the choice moves. A pail that has been opened and closed again keeps for months, so buying the larger one is rarely waste.
Setting-type compound — the kind mixed from a powder — is a different product with a different yield, and this figure is not it. If you are using hot mud for the bed coat and ready-mixed for the finish, work them out separately.
Where the figure comes from, and what it is not
Inch Calculator works compound in pounds per square foot and publishes neither the coefficient nor a source, so there is nothing of theirs to check this against. Omni's drywall page has no compound at all. USG's own estimator has it, which is why the figure here is USG's.
It is one maker's rule of thumb for one product, printed in a FAQ rather than measured off a data sheet, so the page marks it as an estimate and leaves the box open. A taper who knows their own rate should type it in.
Finish levels
The gypsum industry defines six finish levels, Level 0 to Level 5, and a Level 5 skim over the whole surface takes noticeably more compound than a Level 3 wall behind a texture. There is no published gallons-per-square-foot figure per level that we could find, so the page does not pretend to one: it gives the single figure and leaves the box editable. If you are skimming everything, add to it.
Prices are our own estimates, not a store's. We are not connected with any brand or store named here.