Calculator
Example data
| Area (ft²) | Coats | Thickness/coat | Waste | Unit size | Estimated gallons | Units |
|---|---|---|---|---|---|---|
| 80 | 2 | 1.0 mm | 10% | 3.5 gal | 1.57 | 1 |
| 150 | 3 | 1.2 mm | 12% | 5.0 gal | 4.06 | 1 |
| 260 | 2 | 1.5 mm | 15% | 1.0 gal | 5.29 | 6 |
Examples are illustrative; real products vary by brand and application.
Formula used
This mode scales a product’s published coverage to your total thickness.
- TotalThickness = ThicknessPerCoat × Coats
- Gallons = Area × TotalThickness ÷ (CoverageBase × BaseThickness)
- GallonsWithWaste = Gallons × (1 + Waste%)
This mode uses pure geometry and unit conversion.
- CubicInches = Area(ft²) × 144 × TotalThickness(in)
- Gallons = CubicInches ÷ 231
- GallonsWithWaste = Gallons × (1 + Waste%)
Tip: Use coverage mode when your compound label lists coverage at a thickness.
How to use this calculator
- Measure the total area you will spread compound on.
- Select coats and a realistic thickness per coat.
- Enter the product’s coverage and base thickness if available.
- Add a waste percentage for sanding and rework.
- Set unit size and price to get a purchase plan.
- Press Calculate, then download PDF or CSV if needed.
Repair scope and measurement inputs
Accurate drywall planning starts with the finished spread area, not the hole size. Feathering usually expands a small patch into a much larger blend zone, especially under strong lighting. Add seam work, corner repairs, fastener touch-ups, and any skim areas you plan to smooth. Enter the combined surface area, then set coats and thickness per coat to match your target finish quality.
Coverage-based estimating from product specs
Many compounds publish coverage as square feet per gallon at a stated thickness, often near 1/16 inch. Coverage-based mode uses that value and scales it to your total thickness across all coats. This approach tracks real performance when the label data reflects your application method. If you change thickness or add coats, the calculator updates gallons, liters, and purchase units instantly.
Thickness-based estimating using geometry
When product coverage is unknown, thickness-based mode estimates volume from first principles. The tool converts area to square inches, multiplies by total thickness, and converts cubic inches to gallons. This is useful for comparing repair strategies, such as thinner coats with more passes versus fewer thicker coats. It also helps when you are mixing compound types or using specialty fillers.
Waste, density, and jobsite handling factors
Real jobs involve losses from pans, knives, cleaning, sanding, and rework. A 10% waste allowance fits many indoor repairs, while overhead work, textured walls, or first-time finishing can push waste higher. Density is included to estimate carried weight, which matters for ladders and ceilings. If weight is high, plan smaller batches and stage material close to the work area.
Purchasing strategy and workflow efficiency
Packaging varies, so set unit volume to match what you can buy locally. Ceiling rounding is safest for purchasing because running short can interrupt curing and sanding schedules. For tight budgeting, enter unit price and currency to estimate spend, then download PDF or CSV for job notes. After the first coat, revisit thickness and waste inputs using what you observed to refine the second-pass estimate.
FAQs
1) Which method should I use for best accuracy?
Use coverage-based mode when your compound label lists coverage at a thickness. It aligns with real product performance. Use thickness mode when coverage data is unavailable or when comparing different thickness plans.
2) What waste percentage is reasonable for home repairs?
For small patches and seams, 10% is a solid starting point. Tight workspaces, overhead repairs, or first-time users may need 15–20%. Experienced finishers with clean tools can often stay near 5–8%.
3) Why does thickness per coat matter so much?
Volume is proportional to thickness. Doubling thickness roughly doubles required gallons. Thin coats reduce shrinkage and sanding effort, while thick coats may crack or require rework. Consistent, thin passes usually produce better finish quality.
4) How do I estimate area for a patch?
Measure the blended rectangle after feathering, not just the hole. A small hole may need a much larger skim area. Multiply length by width and add areas from other patches to get total coating area.
5) Does this estimate include primer and paint?
No. The calculator estimates repair compound volume, weight, and purchase units. Primer and paint coverage vary by surface and sheen. Use separate coverage tools for primer and paint planning after sanding and dust removal.
6) Why might my real usage differ from the estimate?
Surface texture, tool choice, mixing consistency, and humidity all affect spread rate. Deep fills and multiple sand-and-touch cycles increase usage. Treat the result as a planning number and adjust inputs after your first coat.