Deck Mud Calculator

Estimate dry pack mortar (deck mud) by square feet and thickness. Adjust waste and mix ratio.

Quick guide

Measure your deck mud area (square feet) and average thickness (inches).
Use a coverage chart or rule of thumb to translate thickness into coverage per cubic foot.
Add waste/overage for uneven subfloor, mixing loss, and cleanup (often 5-15%).

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Use the base vs waste volume split to plan how many bags/batches you’ll mix.
Use a common dry pack mortar ratio (often 5:1 sand to cement) and round up.
If you’re building a shower pan, include slope (typically about 1/4" per foot toward the drain) when choosing average thickness.
Plan the waterproofing system first (liner vs bonded membrane). The layer stack affects thickness and materials even if area is the same.
Batch size matters: plan a mixing pace that lets you pack and screed before the mix dries out.

What deck mud is (and what it isn't)

Deck mud (dry pack mortar) is a sand-and-cement mix that's packed and screeded to a flat plane. It's commonly used for shower pans, tile underlayment, and patching low areas where you need a firm, slopeable bed.

It's not the same as thinset, self-leveling underlayment, or concrete. The right product depends on what you're building and the thickness range you need; follow the tile system manufacturer's instructions.

Coverage chart rule of thumb: volume (cu ft) = area (sq ft) x thickness (in) / 12. That means 1 cu ft covers ~12 sq ft at 1", ~6 sq ft at 2", and ~4 sq ft at 3" (before waste).

For shower pans, slope matters. A typical slope target is about 1/4" per foot toward the drain, so the perimeter thickness can be noticeably higher than the drain thickness on larger showers.

Slope or thickness notes: slope is a geometry problem first. Perimeter thickness = drain thickness + (longest run to the drain in feet × slope per foot). Using the longest run (especially with off-center drains) gives a more reliable average thickness input.

Minimum thickness is system-dependent. Some systems require a minimum mud thickness at the drain/flange or over a liner. Confirm minimums before you choose “average thickness” (project dependent).

Workability is the point. Deck mud is mixed fairly dry so it packs and holds shape. Too wet makes it weaker and harder to screed; too dry can make it crumbly and hard to compact.

Different systems want different layers. A traditional liner shower pan often uses a pre-slope + liner + final mud bed. A bonded membrane system may use one sloped bed with a surface membrane. Quantity changes if you add or remove a layer.

Worked example: a 3' x 5' shower (15 sq ft) with an average thickness of 1.5" is 15 x 1.5 / 12 = 1.88 cu ft. Add 10% waste → ~2.1 cu ft. At a 5:1 sand-to-cement ratio by volume, most of that volume is sand.

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Deck Mud Calculator

Estimate dry pack mortar (deck mud) by square feet and thickness. Adjust waste and mix ratio.

Units

Area (sq ft)Thickness (in)Waste/overage (%)Mix ratio preset

Sand : cement ratio

Sand (parts)Cement (parts)

Common deck mud ratios are 5:1 or 4:1 by volume. Use local practice and product guidance.

Results

Base volume (ft3): 12.5
Waste buffer (ft3): 1.25
Total volume (ft3): 13.75
Sand (ft3): 11.46
Cement (ft3): 2.29
Cement bags (94 lb, approx): 3

How to measure for deck mud

Measure the footprint you'll fill (e.g., shower pan) and total the area.
Estimate average thickness: thin edges and thicker slopes change volume.
Convert area x thickness to volume, then split volume by your sand:cement ratio.
If your mix or product lists a coverage chart, use that yield and match the units to your thickness.
If you're building slope, measure the perimeter thickness and the drain thickness, then average them for a more realistic thickness input.
If the drain is off-center, measure thickness at the farthest wall and the closest wall; off-center drains increase the maximum thickness and total volume.
If you will install a pre-slope and a final bed (liner system), estimate each layer separately and add the totals.
If you only know slope per foot, compute perimeter thickness from the longest run and then average perimeter and drain thickness for volume math.

Assumptions to double-check

Deck mud (dry pack mortar) is mixed by volume ratios; products and techniques vary.
Cement bag volume varies by brand; treat bag counts as planning estimates.
If your bed is sloped (typical for showers), thickness is not uniform—use an average.
Coverage charts assume consistent mixing; wetter mixes can reduce coverage and increase waste.
Some systems use a separate waterproofing layer (liner vs bonded membrane). Follow the system instructions—layering affects thickness and materials.
If you need metal lath or reinforcing mesh, it’s a separate material; it won’t change the mud volume much but affects the build and prep.
Dry pack mortar is not a self-leveler. If you need an ultra-flat floor for large-format tile, your system choice may change.

Buying tips

Buy extra sand so you can keep a consistent mix while you work.
Round up cement bags—running short mid-bed can ruin the mix consistency.
Confirm whether you're using masonry sand vs play sand per local practice.
If you're doing a shower pan, confirm drain type and waterproofing system first—those choices often determine the correct build-up and thickness.
Have the right tools: mixing tubs or mixer, straightedges/screeds, level, trowels, and a plan for how you’ll carry and place material quickly.
If your area is large, split work into manageable sections so the mix doesn’t dry out before you pack and screed it.

Common mistakes to avoid

Underestimating average thickness on sloped beds (perimeter and drain thickness both matter).
Mixing too wet, which can reduce pack strength and make screeding harder.
Switching sand types mid-job, which changes workability and consistency.
Trying to use thinset as a thick build-up layer (it's not designed for that thickness range).
Not planning slope and drain height first, then discovering you can’t hit minimum thickness or waterproofing requirements.
Stopping mid-bed and remixing with a different water ratio, creating weak or inconsistent areas.

Last updated: Feb 2026

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Deck mud coverage chart (quick reference)

Coverage is based on simple volume math (before waste): 1 cu ft covers about 12 / thickness(in) sq ft, and 1 cu yd (27 cu ft) covers about 324 / thickness(in) sq ft.

Thickness	Coverage per 1 cu ft	Coverage per 1 cu yd
0.5"	24.0 sq ft	648 sq ft
0.75"	16.0 sq ft	432 sq ft
1"	12.0 sq ft	324 sq ft
1.25"	9.6 sq ft	259 sq ft
1.5"	8.0 sq ft	216 sq ft
2"	6.0 sq ft	162 sq ft
2.5"	4.8 sq ft	130 sq ft
3"	4.0 sq ft	108 sq ft

Tip: If you're building a shower slope, use the average of perimeter thickness and drain thickness, then add a buffer for waste and cleanup.

FAQ

What is deck mud?

Deck mud (dry pack mortar) is a sand-and-cement mix used for mortar beds, often for shower pans and tile underlayment.

How do I calculate deck mud coverage (sq ft)?

Deck mud is a volume estimate: volume (cu ft) = area (sq ft) x thickness (in) / 12. If the bed is sloped (common for showers), thickness is not uniform-use an average thickness, then add a buffer for waste and cleanup.

What mix ratio should I use for deck mud (dry pack)?

Many mixes use 5:1 sand-to-cement by volume as a starting point, but systems vary. Follow your waterproofing/drain system guidance and local practice for minimum thickness and mix requirements (project dependent).

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