Varnish Coverage Converter
Calculate how much varnish or polyurethane you need based on area, number of coats, and product type.
Results in gallons and liters.
Enter your area, select the product type and number of coats to calculate how much finish you need.
Understanding Varnish and Polyurethane Coverage
Varnish and polyurethane coverage varies significantly depending on the product type, application method, wood porosity, and surface condition. Manufacturers provide coverage rates in square feet per gallon (or square meters per liter), but real-world coverage often falls below these numbers, especially on porous or rough surfaces.
Coverage Rates by Product Type:
| Product | Coverage per Gallon | Coverage per Liter | Notes |
|---|---|---|---|
| Oil-based polyurethane | 450-550 sq ft (42-51 m2) | 120-145 sq ft (11-13.5 m2) | Most common floor finish |
| Water-based polyurethane | 500-600 sq ft (46-56 m2) | 130-160 sq ft (12-15 m2) | Faster drying, lower odor |
| Spar urethane (exterior) | 350-450 sq ft (33-42 m2) | 93-120 sq ft (8.6-11 m2) | UV resistant, flexible |
| Marine varnish | 300-400 sq ft (28-37 m2) | 80-106 sq ft (7.4-9.8 m2) | Highest UV and water protection |
| Tung oil | 400-500 sq ft (37-46 m2) | 106-132 sq ft (9.8-12.3 m2) | Penetrating finish |
| Danish oil | 350-500 sq ft (33-46 m2) | 93-132 sq ft (8.6-12.3 m2) | Oil-varnish blend |
| Lacquer (spray) | 400-500 sq ft (37-46 m2) | 106-132 sq ft (9.8-12.3 m2) | Fast drying, thin coats |
| Shellac | 350-450 sq ft (33-42 m2) | 93-120 sq ft (8.6-11 m2) | Traditional finish |
Number of Coats:
Most finishes require multiple coats for proper protection and appearance:
- Floors: 3-4 coats of polyurethane (oil or water-based)
- Furniture: 2-3 coats of polyurethane or varnish
- Exterior wood: 3-5 coats of spar urethane or marine varnish
- Tabletops: 3-4 coats for durability
- Decorative items: 2 coats minimum
First Coat Exception:
The first coat always covers less area because bare wood absorbs more finish. Expect 20-30% less coverage on the first coat compared to subsequent coats. This is especially true for porous woods like oak, ash, and mahogany. Dense woods like maple and cherry absorb less.
Application Method Affects Coverage:
| Method | Coverage vs Rated | Notes |
|---|---|---|
| Brush | 90-100% | Most efficient, some brush marks |
| Foam pad | 85-95% | Good for flat surfaces |
| Roller (foam) | 80-90% | Fast but uses more product |
| Spray (HVLP) | 60-70% | Much lost to overspray |
| Spray (airless) | 50-65% | Most overspray, fastest |
| Wiping (oil finishes) | 95-100% | Best for penetrating finishes |
Calculation Formula:
Gallons needed = (Area × Number of Coats) / Coverage per Gallon
Liters needed = (Area × Number of Coats) / Coverage per Liter
Always round up to the nearest full container size available. It is better to have a small amount left over than to run short mid-coat, which can cause lap marks.
Practical Tips:
- Sand lightly between coats (220-320 grit) for best adhesion
- Allow full drying time between coats (varies by product and conditions)
- Stir varnish gently — never shake, as this creates bubbles in the finish
- Thin the first coat 10-15% with the appropriate solvent for better penetration into bare wood