Drywall Mud Calculator
Calculate how many gallons of joint compound you need for drywall taping over three coats, based on board area, plus total cost.
How this calculator works
Joint compound coverage is estimated at about 1 gallon per 100 square feet of drywall board, accounting for the tape, fill, and finish coats combined. This calculator divides your board area by that rate to estimate gallons needed.
Formula: Gallons = Board area (sq ft) ÷ 100 sq ft per gallon.
Worked example
A wall run 40 ft long x 8 ft tall (320 sq ft of board):
- Area: 40 x 8 = 320 sq ft
- Gallons: 320 ÷ 100 = 3.20 gallons
- At $18/gallon, that’s 3.20 × 18 = $57.60.
Coverage reference
| Board area | Gallons needed (100 sq ft/gal) |
|---|---|
| 80 sq ft | 0.80 gallons |
| 320 sq ft | 3.20 gallons |
| 1,280 sq ft | 12.80 gallons |
How to measure your board area
Use the same total drywall board area you calculated for hanging the sheets — length times height of every wall and ceiling section being taped. Don’t subtract doors and windows unless they’re unusually large, since the compound used at their edges roughly offsets the small savings from the opening itself.
Frequently asked questions
How much joint compound do I need per square foot of drywall?
This calculator uses roughly 1 gallon of joint compound per 100 square feet of drywall board, covering all three standard coats (tape coat, fill coat, and finish coat) combined. That's an average across a typical taping job with average seam density.
Should I buy buckets or boxes of mud?
Pre-mixed joint compound is most commonly sold in 5-gallon buckets (about 61 lbs) or smaller 3.5-gallon boxes. For a whole-house job, buckets are more cost-efficient per gallon; for a small patch or single room, a box may be enough and easier to store.
Does texture or level-5 finish need more mud?
Yes. A smooth level-5 finish that gets a full skim coat over the entire wall uses noticeably more compound than a standard level-4 taped-and-sanded finish, since it adds a thin coat across the full board surface, not just the seams. Budget extra for skim-coated rooms.
Does this include texture spray or primer?
No — this covers taping and finishing compound only. Textured finishes (orange peel, knockdown) use a separate texture compound, and priming the finished wall is a separate material and step entirely.
Estimates only. Verify quantities with your supplier before purchasing.