Deck Mud Calculator
This deck mud calculator works out how much dry-pack floor mud you need for a shower pan or tile bed. Enter the area in square feet and the bed thickness, and it returns the mud volume along with the bags of sand and Portland cement at the standard 5-to-1 recipe.
Quick answer
Deck mud volume is area times thickness, converted to cubic feet.
What this tells you
- •Deck mud volume is area times thickness, converted to cubic feet.
- •Standard deck mud is 5 parts sand to 1 part Portland cement by volume.
- •Finished mud volume is treated as the sand volume, because cement and water fill the gaps between sand grains.
- •Bag counts round up so you do not run short mid-pour.
How to Use
- 1Enter the floor or pan area in square feet.
- 2Enter the finished bed thickness in inches.
- 3Adjust the sand-to-cement ratio if your recipe differs from 5-to-1.
- 4Set your sand bag weight (50 lb is common).
- 5Optionally add a waste allowance, then calculate.
How It Works
Formula
Mud Volume (cu ft) = Area x Thickness(ft)
Sand Volume = Mud Volume x (1 + waste)
Cement Volume = Sand Volume / Ratio
Sand Bags = ceil(Sand Volume x 100 / Bag Weight)
Cement Bags = ceil(Cement Volume x 94 / 94)The calculator converts thickness to feet, computes bed volume, applies any waste allowance, then splits the mix by the sand-to-cement ratio. Sand is estimated at 100 lb per cubic foot and Portland cement at 94 lb per cubic foot (one bag).
Calculation note: values are processed in the order shown above, using the current input units.
Worked Examples
Shower pan, 30 sq ft at 1.25 inches
Floor bed, 100 sq ft at 1.5 inches
Deck Mud per 100 Square Feet (5-to-1 Recipe)
Approximate sand and Portland cement for a 100 sq ft bed at common thicknesses, before waste.
| Thickness | Mud Volume | Sand (50 lb bags) | Cement (94 lb bags) |
|---|---|---|---|
| 1 in | 8.3 cu ft | 17 | 2 |
| 1.25 in | 10.4 cu ft | 21 | 3 |
| 1.5 in | 12.5 cu ft | 25 | 3 |
| 2 in | 16.7 cu ft | 34 | 4 |
Sand at 100 lb per cubic foot, cement at 94 lb per bag. Round up and mix a test batch first.
What Is the Right Deck Mud Ratio?
Deck mud, also called dry-pack or floor mud, is a stiff sand and Portland cement mortar used to build shower pans and level tile beds. The widely used recipe is 5 parts sand to 1 part Portland cement by volume, mixed with just enough water to hold a packed shape when squeezed.
Some installers run as lean as 6-to-1 or as rich as 4-to-1 depending on the sand. Richer mixes are easier to carve but can shrink, so 5-to-1 is the common middle ground. A minimum finished thickness of about 1.25 inches keeps the bed strong enough to resist cracking.
Common mistakes
- Entering thickness in feet instead of inches
- Using a bed thinner than about 1.25 inches
- Forgetting that bag counts are rounded up
- Mixing the mud too wet, which weakens the bed