Wood Finishing Calculator
Calculate how much varnish, oil, wax, paint or stain you need for your project. Shows coats needed, drying time, tins to buy and total cost.
Project Surface
Example: 2m x 1.5m table = 3m² (one side)
Finish Type
Protective clear finish, water & scratch resistant
Typical: 3 coats for this finish
Coverage & Cost
| Surface Area | 5m² |
| Coverage Rate | 12m²/litre |
| Per Coat | 0.42L |
| Total Product Needed (2 coats) | 0.83L |
| Tins to Buy (1L each) | 1 |
| Total Cost | £12.00 |
Drying Time Between Coats
4-6 hours
Estimated Total Project Time
~8 hours (including drying)
Note: Allow extra time for sanding between coats. Final coat should cure for 24-48 hours before use.
Application Tips
- •Always sand lightly between coats for better adhesion
- •Ensure good ventilation during application
- •Stir thoroughly before use, especially for varnish
- •Keep rags/brushes in a sealed container while drying between coats
- •Temperature should be 15-25°C for optimal drying
Coverage by Finish Type
Different wood finishes cover at very different rates per litre. Varnish covers around 12 sq m per litre per coat, oil 15 sq m, wax 20 sq m, paint 10 sq m, stain 15 sq m, lacquer 12 sq m. The default project here, a 5 sq m surface in varnish at 2 coats, needs 0.83 litres of product across both coats - so a single 1-litre tin handles it with leftover for touch-ups. At £12 per litre that is £12 in materials.
Multiply by the number of coats and divide by the tin size to get the buy quantity. Varnish typically wants 3 coats for full build (the default the calculator suggests for varnish), so the same 5 sq m surface needs 1.25 litres total - still one tin in practice but with very little left. For a 20 sq m floor in varnish at 3 coats, you need 5 litres - a 5-litre tin or a 2-litre plus a 5-litre to allow generous waste.
Drying Time Adds Real Hours to a Project
Coverage tells you how much to buy; drying time tells you how long the project will take. Lacquer dries in 15 to 30 minutes, so a 3-coat lacquer job can finish in a single day. Varnish wants 4 to 6 hours between coats, so 3 coats spreads over 1 to 2 days. Oil takes 24 hours between coats and 2 to 7 days to fully cure - a real overnight job at minimum. The calculator estimates total project hours so you can plan when to start.
Sanding between coats also adds time. Most varnishes and paints need a light scuff with 240-grit between coats for adhesion; oils and waxes do not. A 5 sq m surface with 3 coats of varnish, with sanding, is roughly 4 to 6 hours of actual hands-on work spread across 2 days. For the joinery work that often comes before finishing, [Wood Joint Calculator](/wood-joint-calculator) handles the joint dimensions.
Frequently Asked Questions
How much varnish do I need for a table?
A typical 1.6 m by 0.8 m dining table top is about 1.3 sq m. At varnish coverage of 12 sq m per litre per coat, with 3 coats, you need around 0.32 litres total. A 500 ml tin is the smallest economic buy and leaves plenty for touch-ups.
How many coats of varnish do I need?
For a hard-wearing surface (table, floor), 3 coats minimum. For a decorative piece (frame, shelf) 2 coats is usually enough. Each coat builds up the protective film; 3 coats is roughly 25 to 35 microns thick once cured, which resists most household wear.
Oil or varnish for an oak table?
Oil enhances the grain and feels natural to touch but offers less spill protection. Varnish protects better but creates a plastic-feeling surface. A common compromise is hard-wax oil (Osmo Polyx is the leading brand) which combines oil's appearance with reasonable spill resistance. Most modern oak table finishes use hard-wax oil.
How long should I wait between coats?
Varnish: 4 to 6 hours. Oil: 24 hours minimum. Wax: 1 hour, then buff. Paint: 2 to 4 hours. Stain: 2 to 8 hours depending on whether the next coat is stain (2 hours) or sealer (8 hours). Always sand lightly between coats of varnish or paint with 240-grit; oil and wax need no inter-coat sanding.
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