Plaster and joint compound calculator

Figure the dry mix for leveling walls: gypsum plaster, Portland cement plaster or joint compound.

tA
Letters on the drawing match the letters next to the inputs.
sq ft
in
lb
More settings
%
Dry mix365 lb

Shopping list

  • Bags8 bags of 50 lb

How we got there

Consumption used
4.4 lb/sq ft per in
Per area
1.66 lb/sq ft

Results are estimates. Always check the coverage printed on the product and your local building code.

How it is calculated

The amount of mix depends on the area, the average thickness and how many pounds per square foot each inch of thickness takes. Typical values are used by default: about 4.4 lb per sq ft per inch for gypsum plaster and 8.8 for cement plaster or stucco. If your bag lists another figure, choose “Other” and enter it.

FormulaMix, lb = area × thickness × consumption × (1 + extra)Bags = mix ÷ bag weight, rounded up

Example

Leveling 200 sq ft of wall with gypsum plaster at an average of 3/8 in takes about 365 lb with 10 % extra — 8 bags of 50 lb.

Tips from practice

  • Measure thickness with a long level in several places and use the average.
  • Thick coats of gypsum plaster go on in two passes.
  • For skim coats of joint compound enter 1/16 to 1/8 in.

Questions and answers

How much plaster per square foot?

About 1.6 lb per sq ft for a 3/8 in coat of gypsum plaster.

What is the difference between plaster and joint compound?

Plaster builds thick coats on lath or masonry. Joint compound is for thin coats, taping and skim coats on drywall.

Why is stucco so heavy?

Cement-sand mixes are denser than gypsum, so the same coat weighs about twice as much.

Found a mistake in a formula? Write to contact@planicalc.com