The product decides the answer
Most compound calculators give one number. That number is wrong for about
half the people who read it, because the two common all-purpose products
differ by roughly a factor of two.
conventional all-purpose = 125–150 lb per 1,000 ft² of board
lightweight all-purpose = 9–10 gal per 1,000 ft² (72–80 lb), in 4.5 gal / 36 lb pails
compound = board ft² ÷ 1,000 × rate (all three coats)
tape = board ft² ÷ 1,000 × 350 ft
Why the figure is a range
Conventional compound is published as a span rather than a point, and
collapsing it to a midpoint would report a number nobody ever printed.
The headline here is the top of the range, because a taping job that runs
out of mud stops until the merchant opens.
What moves the number most
- Finish level. A Level 5 skim uses far more than a Level 3.
- Joint count. Small broken-up rooms have more joint per square foot than long walls.
- How much you scrape off. Compound applied is not compound left on.
- Product type. The largest single factor, and the one most calculators ignore.
Before the mud
The board goes up first — the
drywall calculator gives sheets
and every consumable in one ticket, and the
drywall screw calculator
covers the fasteners that hold it there.
Compound and tape by sheet count
4 × 8 sheets, three coats. Lightweight pails are 4.5 gal / 36 lb. Conventional is not reported in pails because no pail weight is published for it.
The rest of the job
Compound is one line on a drywall order. The
drywall calculator takes the
same room and works out the board, screws, tape and mud together, the
drywall screw calculator
counts the fasteners on their own, and the
paint calculator covers the
walls once they are finished. If you only have an area, the
square footage calculator
hands it over with a link.
A correction to this page
Conventional all-purpose compound was figured here at 123 to
140 lb per 1,000 ft² of board, from a retailer's estimating
guide. USG publish 125 to 150 for their own product, and since this page
now buys in USG's containers, taking the coverage from one publisher and
the pail size from another produced a bag count neither of them stands
behind. The manufacturer's figure is the one now used. It is about seven
percent more compound, which on many jobs rounds to the same number of
pails and on some — a 2,500 ft² job, for instance — is one more.
Common questions
Can I just give it the room size?
Yes, and that is what it asks for first. The paint calculator has always taken a length, a width and a height; these three asked for a wall area in square feet, for the same room on the same job — so anyone doing both did the multiplication themselves for one of them. Enter the room and it works out the walls as the perimeter times the height. Boarding the ceiling is a separate choice rather than an assumption: plenty of rooms are done to the walls only, and assuming otherwise over-orders by about a fifth. The square footage route is still there for anyone who has an area already.
How much joint compound do I need per sheet of drywall?
Roughly half a gallon per 4 by 8 sheet across all three coats, but the honest answer is that it depends on which product you buy. Conventional all-purpose runs about 125 to 150 pounds per thousand square feet of board. A lightweight all-purpose covers the same board at 72 to 80 pounds — USG publishes it as 9 to 10 gallons per thousand square feet, which is where those pounds come from. Near enough half either way. Pick the type before you work out the quantity, or the number is wrong for one of you.
Why does lightweight compound weigh half as much?
It is formulated with lighter fillers, so the same volume of finished joint weighs considerably less. It sands more easily too, which is why it is common as a finish coat. The coverage is genuinely different, not a marketing figure — which is why this calculator makes you choose rather than averaging the two into a number that fits neither.
How many buckets of mud for a room?
Both types are answered in containers. Lightweight comes in 4.5 gallon pails and 3.5 gallon cartons, and is dosed in gallons, so that is the unit it is bought in. Conventional comes in 48, 50 and 61.7 pound pails, and is dosed in pounds. The calculator sizes on the top of the published coverage range and picks the combination that wastes least, or costs least once you give it a price. Where a size varies by region — 48 and 50 pound pails are the same product in different markets — it is left out of the mix, because a list combining all three is one you cannot fill in one shop.
How much joint tape do I need?
About 350 linear feet per thousand square feet of board. That is an estimating convention rather than a measured constant — the real figure depends on how many joints your sheet layout creates, and a room broken up by openings has considerably more joint per square foot than a long unbroken wall.
Does the number change with finish level?
Yes, substantially. A Level 5 skim coat uses far more compound than a Level 3 that will be textured over. The figures here assume the three coats a normal taped joint gets. If you are skimming the whole surface, treat this as a floor and not a total.
Should I calculate on sheets bought or board hung?
Board hung. You do not tape the offcuts. If you enter a sheet count the calculator multiplies it out to installed area first, which is also why it will not accept a sheet count and an area at the same time — the two would disagree and something would have to be silently discarded.
Sources
- Default waste allowance
- 10%
- Gold Bond Gypsum Board product page (National Gypsum) — panel width 48 in
- Lowe's Drywall Materials Estimator — sheet lengths and per-sheet consumable rates
- USG Sheetrock UltraLightweight All Purpose Joint Compound submittal sheet J2051 — coverage approximately 9 to 10 gallons per 1,000 sq ft of gypsum panels, packaged in 4.5 gal pails, 3.5 gal cartons and 4.5 gal cartons, up to 40 percent lighter than conventional
- USG Sheetrock Brand All Purpose Joint Compound submittal sheet — coverage approximately 125 to 150 lb per 1,000 sq ft of gypsum panels, packaged in 48 lb, 50 lb and 61.7 lb pails and cartons, varying by geographic region
- Grip-Rite coarse thread drywall screws, published SKU table — 1 lb, 5 lb and 25 lb containers; piece counts give 313 per lb at 1 in, 258 at 1-1/4 in, 200 at 1-5/8 in and 175 at 2 in
The 10% allowance is the 1.10 multiplier given in the drywall formula. Screw, tape and compound rates are trade estimating conventions rather than physical constants: they vary with sheet size, framing spacing, finish level and waste, and are always presented as approximate. Fastener spacing is governed by local code and the manufacturer's schedule. Screw counts are ranges because spacing within a schedule is not fixed, and joint compound is split by product type because the two differ by roughly 2x — a lightweight compound covering the same board at about 72 lb per 1,000 ft2 against 123 to 140 for conventional all-purpose. The lightweight figure is now verified against USG's own submittal sheet, and it was wrong: USG publishes 9 to 10 gallons per 1,000 sq ft, which at 4.5 gal and 36 lb per pail is 72 to 80 lb — not the flat 72 stored here, which was the bottom of the band quoted as if it were the whole of it. Coverage is published in gallons rather than pounds, so the gallon figures are stored alongside and are the ones to trust.
Unit conversions are exact by definition and need no source.
How we choose and cite these figures
