Drywall Mud Calculator
Work out how much joint compound (mud) a drywall job needs — litres, gallons and buckets — for a standard 3-coat taped finish.
Mud is the material drywall jobs run out of most often — it is used in three coats, and the quantity is not obvious from the sheet count. This calculator works from the area and a stated coverage rate.
The assumption is printed on the page: 0.41 litres per square metre for a 3-coat finish (1 gallon per 100 ft²), plus your wastage.
Your results
Enter your measurements and press Calculate.
Quantities are rounded up to whole tiles, planks, boxes or bags, after the wastage allowance. Cost appears only when you enter a price.
Formula
All lengths are converted to a single unit before the calculation: 1 ft = 0.3048 m, 1 in = 25.4 mm, 1 ft² = 0.09290304 m², 1 yd² = 9 ft². Material quantities are rounded up — you cannot buy part of a tile, plank or bag.
How to use this calculator
- Enter the drywall area if you know it, or the room size.
- Choose whether the ceiling is included.
- Set wastage at 10%.
- Add a price per bucket if you want a cost estimate.
Worked example
| Area | 612 ft² (12 × 15 ft room, walls + ceiling) |
|---|---|
| In square metres | 612 × 0.09290304 = 56.86 m² |
| Compound | 56.86 × 0.41 = 23.31 L |
| With 10% wastage | 23.31 × 1.10 = 25.64 L = 6.77 gal |
| Buckets (5 gal = 18.93 L) | ⌈25.64 ÷ 18.93⌉ = 2 buckets |
Check it by hand: every step above uses the formula in the box. If your numbers match the example inputs but the calculator gives a different answer, please report it via the contact page.
Frequently asked questions
How much drywall mud do I need?
About 0.41 litres per square metre of drywall (1 gallon per 100 ft²) for a standard 3-coat taped finish, plus 10% wastage. A 12 × 15 ft room (walls + ceiling) needs about 6.8 gallons — 2 buckets of 5 gallons.
What is drywall mud?
Joint compound — the paste used to tape and fill the joints between drywall sheets, and to cover screw heads, in three coats (tape, fill, finish). It is sold ready-mixed in buckets, usually 5 gallons.
How many coats of mud?
Three: a tape coat (embedding the joint tape), a fill coat, and a finish coat, each wider than the last. Each coat must dry before the next — allow a day between coats.
Can I use the same mud for the whole job?
Yes — one all-purpose ready-mixed compound does taping, filling and finishing for most jobs. Setting-type compound (powder) dries faster and is better for deep fills.
Related calculators
Estimates only. Results are for planning. Measure twice, confirm box coverage and tile sizes on the packaging you buy, and follow the manufacturer's instructions. See the disclaimer.