Plaster Calculator

Coverage varies by type and thickness: Gypsum plaster covers 35-45 sq ft (3.5-4.5 m²) per 25 kg bag at 12mm thickness. Cement plaster covers 20-30 sq ft (2-3 m²) per bag at 20mm. Stucco (all 3 coats) needs about 15-20 sq ft (1.5-2 m²) per bag. Add 10-15% for waste and uneven surfaces.

Gypsum plaster is interior-only, smooth finish, quick-setting. Cement plaster is durable, water-resistant, good for exterior. Stucco is textured cement for exterior walls in 3 coats (scratch, brown, finish). Lime plaster is breathable, traditional, good for historic buildings. Choose based on location (interior/exterior) and finish requirements.

Plaster costs: USA $2-6/sq ft installed; UK £12-25/m²; EU €15-30/m²; India ₹15-40/sq ft; Australia A$25-50/m². Materials alone: $8-15 per 25kg bag. Stucco costs more due to 3-coat process. Labor is typically 60-70% of total cost. DIY saves significantly but requires skill for smooth finish.

Interior gypsum: 10-15mm (3/8-5/8") total. Cement plaster exterior: 15-20mm (5/8-3/4"). Stucco: 7/8" total (scratch 3/8", brown 3/8", finish 1/8"). On masonry, single coat 12-15mm. On lath, two coats 3/4" total. Thicker isn't better—proper thickness ensures strength without cracking. Follow manufacturer specifications.

For cement plaster at 1:4 ratio (cement:sand), 1 bag cement needs 4× volume of sand (about 0.12 m³ or 4 cu ft). For 100 sq ft at 3/4" thick: approximately 2 bags cement + 0.25 m³ sand. Pre-mixed products simplify calculation—just add water. Plastering sand should be clean, well-graded, and free of organic matter.

Gypsum plaster sets in 20-30 minutes but needs 24-48 hours before painting. Cement plaster takes 24 hours initial set, 7 days to cure, 28 days full strength. Keep cement plaster moist for first 7 days (curing). Don't apply subsequent coats until previous is set. Temperature and humidity affect drying—avoid freezing or extreme heat.