0.2 Inch Plaster Coat - How Many Bags Do You Need?

Cement, gypsum, acrylic - three materials, three consumption rates

The same wall plastered with three different materials requires three very different quantities. Cement render consumes 1.75 kg per mm per m2. Gypsum plaster drops to 1.1 kg. Acrylic finish jumps to 2.75 kg. For a 200 sq ft wall (e.g. 25 x 8 ft), two coats at 0.5 in thickness each take 34 bags of cement render (55 lb each). Switch to gypsum and that drops to 21 bags. Go acrylic and it climbs to 53 bags. This calculator covers all three types - enter the wall, pick the plaster, set thickness and coats, read the bag count.

Plaster type atlas

Type	Rate (kg/mm/m2)	Typical thickness	Best for	Cost ($/bag)
Cement render	1.75	0.4-0.8 in	Exterior walls, basements, wet areas	$8-15
Gypsum plaster	1.1	0.2-0.6 in	Interior walls, ceilings, skim coats	$10-18
Acrylic finish	2.75	0.1-0.3 in	Decorative finishes, EIFS, facade renovation	$25-50

Thickness guide by application

Application	Thickness	Coats	Notes
Skim coat (drywall finish)	0.1-0.2 in	1	Gypsum only. Smooths joints and imperfections
Standard interior wall	0.4-0.6 in	2	Scratch coat + finish coat
Uneven masonry	0.8-1.2 in	2-3	Thick buildup to level rough walls
Exterior cement render	0.6-1.0 in	2-3	Weather protection. Often with mesh reinforcement
Decorative acrylic	0.1-0.2 in	1-2	Thin finish over base coat. Texture or smooth

How to use - step by step

Wall length - for a single wall, measure its length. For an entire room, add all four walls (e.g. 16 + 12 + 16 + 12 = 56 ft).
Wall height - measure floor to ceiling. Standard US home: 8 ft.
Windows and doors (optional) - subtract their area. Typical window: 15 sq ft. Typical door: 21 sq ft.
Plaster type - cement render for exteriors and wet areas. Gypsum for interior walls. Acrylic for decorative finishes.
Layer thickness - skim coat: 0.1-0.2 in. Standard: 0.4-0.6 in. Heavy render: 0.8-1.2 in.
Number of coats - one for skim. Two for standard. Three for precision or thick buildup.
Prices (optional) - per bag and per sq ft labor for total project cost.
Read results - total weight, bag count, comparison across all three plaster types.

Practical examples

Example 1: Bedroom wall - 14 x 8 ft, no openings, gypsum, 0.4 in, 2 coats
Need: 513 lb - 10 bags (55 lb each)

Example 2: Full room - 56 x 8 ft perimeter (16x12 room), minus 36 sq ft openings, cement render, 0.6 in, 2 coats
Need: 4,502 lb - 82 bags. At $12/bag = $984

Example 3: Garage exterior - 24 x 10 ft, cement render, 0.8 in, 2 coats
Need: 3,496 lb - 64 bags

Example 4: Ceiling skim coat - 14 x 12 ft (entered as 14 length, 12 height), gypsum, 0.15 in, 1 coat
Need: 144 lb - 3 bags

Example 5: Accent wall - 10 x 8 ft, acrylic finish, 0.15 in, 2 coats
Need: 343 lb - 7 bags. At $35/bucket = $245

FAQ - Frequently asked questions

How many bags of plaster for a 10x12 room?

A 10 x 12 ft room with 8 ft ceilings has about 352 sq ft of wall (perimeter: 44 ft x 8 ft). Subtract roughly 36 sq ft for a window and door = 316 sq ft net. With gypsum plaster at 0.5 in thickness, 2 coats: about 33 bags (55 lb each). Cement render for the same wall: 53 bags.

Can I plaster over painted walls?

Not directly. Paint creates a smooth, non-absorbent surface that plaster cannot grip. First sand the wall to roughen it, then apply a bonding agent (PVA or acrylic primer). Alternatively, apply a scratch coat of cement render with bonding agent mixed in, let it cure, then skim with gypsum. Total thickness adds up - plan for 0.3-0.5 in extra.

How long does plaster take to dry?

Gypsum: sets in 30-90 minutes, ready to sand in 24 hours, ready to paint in 3-7 days. Cement render: initial set in 2-6 hours, cures over 28 days (keep moist for the first 7). Acrylic: touch-dry in 2-4 hours, fully cured in 24-48 hours. Temperature and humidity affect all three - do not plaster below 40 F (5 C).

What is the difference between plaster and stucco?

Functionally, they are the same material - cement, sand and water. Stucco is the term used for exterior cement render in North America, usually applied in three coats (scratch, brown, finish) over metal lath. Plaster typically refers to interior gypsum-based finishes. This calculator works for both - select "Cement render" for stucco projects.

Do I need mesh reinforcement?

Mesh (fiberglass or metal lath) is required in three situations: (1) plastering over two different materials (e.g. masonry meets drywall), (2) exterior stucco over wood framing, (3) thick coats over 1 inch that risk cracking. For standard interior gypsum skim coats, mesh is not needed. Budget $0.20-0.50/sq ft for fiberglass mesh.

How much does professional plastering cost?

Materials only: $0.50-2.00/sq ft depending on type and thickness. Professional labor: $2-8/sq ft on top. A 300 sq ft room (materials + labor) typically costs $750-3,000. Skim coating is cheapest. Three-coat stucco is most expensive. Machine application is faster and sometimes cheaper per sq ft than hand troweling.

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