STUCCO BAGS
About this calculator
This stucco calculator estimates 80-lb bag count for an exterior stucco job. Traditional 3-coat (scratch + brown + finish) burns roughly one 80-lb bag per 8 ft² for the scratch coat, another for the brown coat, and one per 12 ft² for the finish coat — about 38 bags per 100 ft² of wall. One-coat synthetic systems run closer to one bag per 12 ft² total. The calculator subtracts window and door area, applies a 10% waste factor, and returns bag counts by coat plus the metal lath sheets needed underneath. ESTIMATE ONLY — exact yields vary by mix design and lath substrate; verify with the manufacturer.
How to use this calculator
Enter wall length and height in feet, then subtract any window/door opening area. Pick the stucco system: 3-coat traditional (scratch + brown + finish) gives the longest service life and is the residential standard for new construction; 1-coat / synthetic systems are faster to install and more common in commercial or remodel work but cost more per bag.
The calculator returns bag count by coat (for 3-coat) or total bags (for 1-coat) plus the metal lath sheets needed underneath. Stucco is applied over self-furring metal lath nailed to wood-framed walls or directly bonded to CMU/masonry substrates.
Worked example
For a 30 × 8 ft wall with 60 ft² of openings, 3-coat traditional stucco:
Net wall area: 240 - 60 = 180 ft². With 10% waste: 198 ft².
Scratch coat (~1 bag per 8 ft²): ⌈198 ÷ 8⌉ = 25 bags. Brown coat (same): 25 bags. Finish coat (~1 bag per 12 ft²): ⌈198 ÷ 12⌉ = 17 bags. Total: 67 bags of 80-lb stucco mix.
Metal lath: ⌈180 ÷ 18⌉ = 10 sheets of 27"×96".
At $10-$15 per bag of stucco mix and $25-$40 per lath sheet: materials cost $670-$1,005 (stucco) + $250-$400 (lath) = $920-$1,405 for the wall. Add corner aids, weep screed, and accessories ($100-$200) and DIY material total runs $1,000-$1,600.
Switching to 1-coat synthetic on the same wall: ⌈198 ÷ 12⌉ = 17 bags total = $200-$300 in stucco. The 1-coat saves dramatically on materials but costs $1.50-$3 more per bag for the polymer-modified mix.
Common mistakes & waste factors
Skipping the scratch coat. The scratch coat is the bonding layer — without it, brown and finish coats slip off the lath in big sheets within months. Never skip it on traditional 3-coat.
Applying in cold weather. Stucco shouldn't cure below 40°F. Cover finished walls with insulated tarps or wait for warmer weather. Cold-cured stucco fails within years.
Underwatering during cure. Stucco needs misting twice daily for the first 2-3 days to prevent shrinkage cracks. Skipping the cure water is the #1 cause of hairline cracks in new stucco.
Forgetting expansion joints. Walls over 144 ft² or 18 ft in any direction need expansion joints to absorb thermal movement. Without them, stucco cracks at corners and over openings within a year.
Rules of thumb
3-coat traditional: ~38 bags of 80-lb mix per 100 ft² (scratch ~12.5 bags, brown ~12.5, finish ~8.5).
1-coat synthetic: ~8 bags per 100 ft².
Metal lath: 27"×96" sheets = 18 ft² each. 1 sheet per 18 ft² of wall.
Stucco cure: mist twice daily for 2-3 days minimum. Faster cure = more shrinkage cracks.
Apply at 40-90°F, no rain forecast 24 hours minimum.
Expansion joints required at 144 ft² or 18 ft in any direction.
Finish coat is the only one with color — pigmentation is integral to the mix, not painted on.
Common questions
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