Fence Stain Calculator

coated area = length × height × sides then stain = coated area × coats ÷ coverage

L

Length of the fence run, in feet

H

Height of the fence, in feet — the height of the boards, not the height including the posts above them

sides

Sides coated: 1 for the face only, 2 for both faces (the usual answer on a wood fence)

c

Coverage on the can, in square feet per gallon per coat (300 for a transparent oiling stain, 150 for a solid colour on old wood)

n

Number of coats — two is the usual job outdoors

coated area

The area that actually gets stain, in square feet — already multiplied by the number of sides but not by the coats

Measure the run and the board height, then answer the sides question honestly before you buy anything. Two sides is the normal answer for a wood fence and it is the page default; one side is what people do when the back is against a hedge or a neighbour they never speak to, and it doubles the risk of cupping boards. Read the can next, because the coverage figure is a field rather than a constant and the same stain spreads twice as far on new wood as on a fence that has been grey for years. A fence that is already coated usually needs one refresher coat; bare new wood wants two. This page treats the fence as a solid panel, so if your fence is pickets with gaps between them, the area it reports is on the high side — how much high depends on the gap.

1. A 100 ft × 6 ft wood fence, both sides, two coats

   1. One side: 100 × 6 = 600 sq ft
   2. Both sides: 600 × 2 = 1,200 sq ft (111.48 m²)
   3. Stain: 1,200 × 2 coats ÷ 300 = 8 gallons exactly
   4. In litres: 8 × 3.785 = 30.28 L, rounded up to 31

   These are the page defaults, and the arithmetic lands exactly on 8 gallons — which is the one case where you cannot tell from the result whether you should buy 8 or 9. You should buy 8, but not much less than 8: the same fence read at the low end of the table — 150 sq ft per gallon, which is where a fence that has weathered grey for years lands — comes to 16 gallons. The litres disagree with the gallons on purpose: 8 gallons is 30.28 litres, so a supplier selling litres will hand you 31 of them.

2. A 50 ft × 4 ft fence, both sides, a single refresher coat

   1. One side: 50 × 4 = 200 sq ft
   2. Both sides: 400 sq ft (37.16 m²)
   3. Stain: 400 × 1 coat ÷ 250 = 1.6 gallons, rounded up to 2
   4. In litres: 1.6 × 3.785 = 6.06 L, rounded up to 7

   A low fence with one coat is where the rounding-up hurts most in proportion: 1.6 gallons becomes 2, so a fifth of what you buy is margin. It is still the right way round — coming back for a second can mid-fence leaves a visible join where the two batches meet, and stain from a different batch can read as a different colour even when the code matches.

3. The same 100 ft fence, face only

   1. One side only: 100 × 6 = 600 sq ft (55.74 m²)
   2. Stain: 600 × 2 ÷ 300 = 4 gallons
   3. In litres: 4 × 3.785 = 15.14 L, rounded up to 16

   Half the fence, half the stain — sides is the one field on this page with only two settings, and moving it doubles the whole bill. The saving is real money on a long run, but it comes with a physical cost: a board that is sealed on one face and bare on the other takes up water unevenly and cups towards the dry side, which is how pickets end up with gaps opening between them a season later.

This page multiplies an area and divides by a coverage figure. It treats the fence as a solid panel, so on a picket fence with gaps between the boards the area it reports is larger than the wood actually there — typically 20% to 30% high on a fence with wide picket gaps, and within about 5% on a butted privacy fence. That error is deliberate and it is in the safe direction: you may buy more than you need, but you will not run out halfway. It also does not know your stain. The coverage figure is an input, the four rows in the reference table are typical values rather than guarantees, and a fence that has weathered grey for years takes the first coat like a sponge — read the low end of the table for old wood. Nor does it count the parts of a fence that are not the flat run: posts, rails, the top cap and any trim are all coated surfaces this page never sees. It does not account for preparation, which decides the outcome more than the arithmetic does — a fence must be cleaned and dry, and coating over a failing film-forming finish will peel within a season. Finally, gallons and litres round up separately to whole containers, so 8 gallons and 31 litres on the same result are both correct and are not the same amount of liquid.

How much stain do I need for 100 ft of 6 ft fence?

8 gallons of a transparent oiling stain at 300 sq ft per gallon, for two coats on both sides. The fence is 600 sq ft per side and 1,200 sq ft for two sides, and 1,200 × 2 ÷ 300 = 8 gallons exactly. In litres that is 30.28, which rounds up to 31. With a solid colour at 150 sq ft per gallon the same fence takes 16 gallons instead of 8 — twice the stain for the same wood.

Do I really have to stain both sides?

It is the usual advice and it is the page default, for two reasons. The back of a fence weathers just as much as the front, so coating one side only means the other is bare within a season. And a board sealed on one face and bare on the other takes up water unevenly and cups towards the dry side, which opens gaps between pickets. Where the back is genuinely sheltered — tight against a building or a hedge — one side is a reasonable call, and the page will halve the answer for you.

Why does the page report 8 gallons and 31 litres?

Because they are two different containers, each rounded up on its own. 8 gallons is 30.28 litres, so the litre figure becomes 31 — and 31 litres is 8.19 gallons. Neither number is a conversion of the other; they are two shopping lists. Buy whichever unit your supplier stocks and read that row, and do not try to reconcile the two.

My fence is pickets with gaps. Is the area wrong?

It is on the high side, yes. This page treats the fence as a solid panel, so a picket fence with wide gaps has less wood than the area it reports — often 20% to 30% less. That was a deliberate choice: you would need the picket width and the gap to correct it, and on a fence those are set on site rather than known in advance, so a field asking for them would be a false precision. Buying a little extra is the safe direction. On a butted privacy fence the error is under 5%.

One coat or two on a fence?

Two on bare or new wood, one as a refresher on a fence that is already coated — which is what the coats field is for. The first coat on dry wood is largely absorbed and does not build a surface, so a single coat on new boards leaves the grain raised and unprotected; a second coat is what gives the colour and the water resistance. The page treats coats as a multiplier on the stain, not on the area, so changing it moves the gallons and litres and leaves the two area rows alone.

How accurate is the coverage figure?

It matters more than anything else on the page, and it is the number you have least control over. The four typical values run from 150 to 300 sq ft per gallon, a factor of two, and the wood can move the real figure by as much again: new cedar and a fence that has been grey for five years behave completely differently under the same can. Use the number printed on your can, and on weathered wood go to the low end of the table rather than the middle. If you end up with a little left over, that is the right side to err on.

• Approximate Conversions from U.S. Customary Measures to Metric — the square-foot to square-metre figures reported on this page — National Institute of Standards and Technology
• Lumber — nominal and actual dimensions, and the board widths whose two faces this page counts — Wikipedia