Plaster Calculator
Estimate plaster bags from wall area, coat thickness, product coverage, waste, and bag price for veneer plaster, gypsum basecoat, finish coat, or stucco.
How the plaster estimate is calculated
Search results for English plaster calculators focus on square footage, coat thickness in inches, product coverage or bag yield, and a waste allowance. This calculator follows that buying workflow instead of using a regional kilograms-per-square-meter norm.
A net - net surface area, A gross - measured wall area, A openings - windows, doors, and skipped areas.
C eff - adjusted coverage, C ref - coverage per bag at the reference thickness, T ref - reference thickness, T - planned coat thickness.
N - bags to buy, A net - net area, r - waste percentage, C eff - adjusted coverage per bag.
- Measure wall width and height in feet or enter a known square-foot area
- Subtract windows, doors, repairs you are not coating, and other openings
- Choose the plaster type that matches the product data sheet
- Enter coverage per bag and the thickness that coverage assumes if your product label differs
Coverage assumptions by plaster type
| Product type | Typical bag | Reference coverage | Reference thickness |
|---|---|---|---|
| Veneer plaster basecoat | 50 lb | about 90-110 sq ft | 1/16 in |
| Veneer plaster finish coat | 50 lb | about 135-160 sq ft | 1/16 in |
| Gypsum basecoat plaster | 50 lb | about 30-40 sq ft | 3/8 in |
| Portland cement stucco base coat | 80 lb | about 24 sq ft | 3/8 in |
Veneer plaster, basecoat, and stucco are different jobs
| Use case | Common thickness | Notes |
|---|---|---|
| Veneer plaster over gypsum base | about 1/16 in per coat | Often specified as a basecoat plus finish coat system |
| Conventional gypsum basecoat | about 3/8 in or more | Use the system specification for lath, base, and finish |
| Stucco scratch or brown coat | about 3/8 in per coat | Coverage is often derived from cubic yield per 80 lb bag |
| Patch or skim work | varies | Small repairs need product-specific coverage more than generic wall-area math |
Waste, openings, and buying notes
A 5-10% waste allowance is common for clean rectangular walls. Use 10-15% for many openings, uneven substrates, corner work, small repairs, or first-time application.
Openings should be subtracted only when they are large enough to matter. Around windows, doors, corners, and patches, some saved area is offset by extra trowel work and edge loss.
Frequently Asked Questions
Sources and References
- Diamond Veneer BasecoatUSG
- Gold Bond Kal-Kote Basecoat PlasterGold Bond Building Products
- QUIKRETE Scratch and Brown Base Coat StuccoQUIKRETE
- ASTM C842 Standard Specification for Application of Interior Gypsum PlasterASTM International
Calculations are based on the listed reference sources. Links open in a new tab.
Related Tools
Estimate interior wall paint from room dimensions, doors, windows, coats, coverage per gallon, waste allowance, and optional price.
Estimate wallpaper rolls for a room using wall dimensions, US roll sizes, pattern repeat, doors, windows, and waste.
Estimate shiplap, tongue-and-groove, beadboard or wall paneling boards from wall size, exposed face width, board length, openings, waste, packs and cost.
Estimate tiles, boxes, square footage, waste, thinset, grout and material cost for one rectangular floor, wall or backsplash surface.