Stucco Calculator
A stucco calculator divides wall area by 25 sq ft per 80-lb bag at a 3/8 in coat. A 20 × 8 ft wall is 160 sq ft and takes 7 bags, or $84.
A stucco calculator estimates how many 80-lb bags of stucco mix cover a wall. One bag covers about 25 sq ft at a 3/8 inch coat. A 20 ft by 8 ft wall is 160 sq ft, so 160 ÷ 25 = 6.4 bags, which rounds up to 7. At $12 per bag that is $84.
The formula in plain words
Find the wall area. Divide by 25, the square feet one bag covers at 3/8 inch. Round up to a whole bag.
The coverage depends on thickness. Spread the same bag at half the depth and it covers twice the area. The 25 sq ft figure assumes one 3/8 inch coat, so a thicker or thinner coat changes the count.
Worked examples
Example 1, the default: a wall 20 ft long and 8 ft high, $12 per bag.
- Area: 20 × 8 = 160 sq ft
- Bags: 160 ÷ 25 = 6.4, rounded up to 7
- Cost: 7 × $12 = $84
Example 2, a house wall with openings: 40 ft long and 9 ft high, with two 3 × 4 ft windows and one 3 × 7 ft door.
- Gross area: 40 × 9 = 360 sq ft
- Windows: 2 × 12 = 24 sq ft. Door: 21 sq ft
- Net area: 360 − 24 − 21 = 315 sq ft
- Bags: 315 ÷ 25 = 12.6, rounded up to 13
- Cost: 13 × $12 = $156
Bags by wall area
| Wall area | Bags (rounded up) | Cost at $12 |
|---|---|---|
| 96 sq ft | 4 | $48 |
| 128 sq ft | 6 | $72 |
| 160 sq ft | 7 | $84 |
| 300 sq ft | 12 | $144 |
| 360 sq ft | 15 | $180 |
| 800 sq ft | 32 | $384 |
How to measure
In this calculator, enter the wall length in the first box and the wall height in the second. Multiply the two for the gross area, then subtract windows and doors. Do each wall separately and add the bag counts, or add the areas first and divide once.
Remember that the sides of window and door openings, corners, and the bottom edge of the wall take extra material to finish, so do not subtract every opening down to the last inch.
Thickness and coats
The 25 sq ft rate is for one 3/8 inch coat. A traditional three-coat job builds up scratch, brown, and finish layers, and the total is thicker than one coat. Work out the total thickness from the product’s instructions, then compare it with 3/8 inch to scale the bag count. A buildup twice as thick needs about twice as many bags.
Mix only what you can apply before it sets, and follow the bag instructions for water, curing, and temperature.
Common mistakes
- Treating the number as the full system. Lath, paper, and finish coats all count.
- Measuring only the front of the house.
- Ignoring the existing wall condition. An uneven wall takes more material to bring it flat.
- Mixing too much at once. Stucco stiffens, and a bag mixed too early is wasted.
- Skipping the curing steps on the bag. Fast drying in hot, windy weather causes cracks.
Hauling and storing the bags
For the 40 × 9 ft house wall, 13 bags at 80 lb weigh 13 × 80 = 1,040 lb, a bit over half a ton. Plan the delivery and where the pallet sits. Keep the bags dry and off the ground, since moisture sets the mix in the bag. Check the date, because old bags may not cure properly.
Working in sections
Stucco is applied wet and finished in one go, so large walls are planned in sections that end at natural breaks, such as corners or trim. Estimate each section’s bags separately so you know how much to mix per day. Because the count rounds up per run, adding the sections’ areas first and then dividing gives a closer total than summing the rounded bags.
Related calculators
For repairs, the stucco repair cost calculator prices patching. The concrete block calculator and the brick calculator cover walls that stucco might go over, and the mortar calculator handles the joints.
Frequently asked questions
How many bags of stucco do I need for a wall?
Divide the wall area by 25 and round up, since one 80-lb bag covers about 25 sq ft at a 3/8 inch coat. A 20 × 8 ft wall is 160 sq ft, which is 6.4 bags, so you buy 7. At $12 per bag that is $84.
Does this cover a full three-coat stucco system?
No. It estimates one coat at 3/8 inch. A three-coat system applies scratch, brown, and finish coats over lath, and the total buildup is thicker, so the material needed is a multiple of one coat. Coverage scales with thickness: a coat twice as thick covers half the area per bag.
What's the difference between one-coat and three-coat stucco?
Three-coat is the traditional system over metal lath: scratch, brown, then a finish coat. One-coat systems use a single, thicker application over a sheathing and lath or a bonded base, sold as a proprietary product. Which one a wall uses depends on the existing structure and the product maker's instructions.
Why isn't there a waste allowance for stucco?
The count already rounds up to whole bags, and the 25 sq ft per bag rate is a planning average. If your walls have many windows, corners, or an uneven base, add a bag or two by hand. Keep in mind that mixed stucco cannot be stored.
Does this include the wire lath or scratch coat base?
No. It counts stucco mix only. Lath, building paper, trim accessories, color coat, and sealer are separate. Applying stucco well takes skill, so for a large wall consider a plasterer.
Estimates only. Verify quantities with your supplier before purchasing.