The short answer: a 100 ft by 6 ft fence needs about 3 gallons of stain for one coat on one side at a typical 200 sq ft per gallon, or roughly 12 gallons for both faces with two coats. Here is the math.
The formula
total area = length × height × sides × coats × roughness gallons = total area ÷ coverage per gallon, rounded up
A 100 ft by 6 ft fence is 600 sq ft on one face. Covering both faces doubles it to 1,200 sq ft. Two coats doubles it again to 2,400 sq ft. At 200 sq ft per gallon, that is 2,400 ÷ 200 = 12 gallons.
What changes the number
Sides. A boundary fence you only finish on your side uses half the stain of a fence you coat front and back.
Coats. Semi-transparent and solid stains usually want two coats. The first coat on bare wood always drinks the most.
Wood condition. Rough-sawn, old or weathered boards have more surface area and absorb more. Plan for about 1.5 times the smooth figure.
| Job | Area to cover | Gallons at 200 sq ft/gal |
|---|---|---|
| One side, one coat | 600 sq ft | 3 |
| Both sides, one coat | 1,200 sq ft | 6 |
| Both sides, two coats | 2,400 sq ft | 12 |
Check the can
Coverage varies by product. A thin penetrating oil might stretch to 250 sq ft per gallon; a solid-colour stain on rough wood can drop below 150. Use the figure printed on the can rather than a guess, and buy whole gallons so a little is left for touch-ups.
Get your exact number
Enter the length, height, sides, coats and your product’s coverage in the fence stain calculator and it returns the gallons to buy. To size the fence itself first, the wood fence guide counts the posts, rails and pickets.