Project Inputs
Formula Used
Material (kg) = Area (m2) × Thickness (mm) × Coverage (kg/m2/mm) × Coats × (1 + Wastage% ÷ 100)
Bags = ceil(Material (kg) ÷ Bag size (kg))
Grand total = Material cost + Labor cost + Primer cost (optional)
Coverage and consumption vary by product, substrate, and finish quality target.
How to Use This Calculator
- Measure the net area to be skim coated in square meters.
- Enter the average skim thickness and the planned number of coats.
- Use the product coverage value from the datasheet.
- Add a wastage percentage for mixing and surface irregularities.
- Enter bag size and pricing to estimate material cost.
- Add labor rate per square meter per coat for installed cost.
- Optionally include primer consumption and pricing.
- Press Calculate, then download CSV or PDF if needed.
Skim Coat Planning Guide
Purpose of a skim coat
A skim coat is a thin leveling layer used to improve flatness and appearance before painting or decorative finishes. Better estimating prevents shortages, minimizes re-mixing, and supports consistent quality.
Key inputs that drive quantity
Quantity depends on net area, average thickness, number of coats, and the coverage factor in kilograms per square meter per millimeter. Because thickness varies across a wall, use a practical average. Add a wastage allowance to cover mixing losses, tool residue, and extra filling on low spots.
Interpreting coverage and thickness
Coverage varies by product and application method. Material use increases proportionally with thickness and coats. For high-end paint finishes, two coats usually reduce visible defects and lower rework after sanding.
Surface preparation and curing
Remove dust and loose material, then patch deep voids before skimming. On porous surfaces, primer can control suction and improve bond. Follow drying guidance between coats; sanding too early can tear the surface, while sanding too late increases labor.
Cost drivers beyond bags
Installed cost commonly includes material, labor, and optional primer. Labor scales with area and coats because each coat involves spreading, checking hollows, and touch-up sanding. Primer may reduce finish risks on uncertain substrates. Plan room sequencing so drying time does not delay painting.
Worked example with project data
For 120 m2 at 2 mm, 2 coats, coverage 1.10 kg/m2/mm, and 10% wastage, the estimate is 580.80 kg. With 20 kg bags, that rounds to 30 bags, matching the first row in the example table below.
Quality control checkpoints
Use a light and straightedge after the first coat to spot ridges and low areas. Track actual bag use on the first room and adjust thickness or wastage for the remaining areas. This simple check reduces surprises on larger jobs.
Practical tips for better accuracy
- Measure net area and subtract large openings when possible.
- Increase wastage for first-time crews and difficult access.
- Validate coverage with a small trial on a representative surface.
- Order a small contingency when schedule risk is high.
- Store bags dry and mix consistent batches for smoother work.
Example Data Table
| Area (m2) | Thickness (mm) | Coats | Coverage (kg/m2/mm) | Wastage (%) | Bag (kg) | Estimated material (kg) | Estimated bags |
|---|---|---|---|---|---|---|---|
| 120 | 2 | 2 | 1.10 | 10 | 20 | 580.80 | 30 |
| 75 | 1.5 | 2 | 1.00 | 8 | 25 | 243.00 | 10 |
| 40 | 1 | 1 | 1.15 | 5 | 20 | 48.30 | 3 |
Examples are illustrative; verify coverage with your selected product.
Use results to order materials and schedule crews wisely.
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