A fence is one of the first things to weather, and a coat of stain or sealer every couple of years keeps it from turning grey and splitting. Buying the right amount matters: too little and you stop halfway, with a colour match to worry about; too much and you pay for a spare can. This calculator turns the size of the fence and the coverage rate printed on the can into gallons.
How to use the fence stain calculator
- Enter the length and height of the fence.
- Pick one side or both sides and choose a style: solid privacy boards cover the whole plane, open styles cover less.
- Enter the coverage per gallon from the product label.
- Set the number of coats and a percentage extra for rails, posts and spills.
Fence stain formula
Gallons = area × coats × (1 + extra) ÷ coverage per gallon
The style share is 100% for a solid fence and lower for pickets and shadowbox designs, where gaps reduce the stained surface. The coverage rate is the biggest variable: a smooth, sealed surface takes less stain per square foot than raw, rough-sawn or very dry boards that soak up product.
Worked example: a 100 ft by 6 ft privacy fence, both sides
- One side: 100 × 6 = 600 sq ft. Both sides: 1200 sq ft.
- At 150 sq ft per gallon: 1200 ÷ 150 = 8.0 gallons for one coat.
- Add 10%: 8.8 gallons, so buy 9 gallons, or one 5-gallon pail and some one-gallon cans.
Gallons for 6 ft fences, both sides, one coat
| Fence | Surface (sq ft) | At 100 sq ft/gal | At 150 sq ft/gal | At 250 sq ft/gal |
|---|---|---|---|---|
| 50 ft × 6 ft | 600 | 6.0 | 4.0 | 2.4 |
| 100 ft × 6 ft | 1200 | 12.0 | 8.0 | 4.8 |
| 150 ft × 6 ft | 1800 | 18.0 | 12.0 | 7.2 |
| 200 ft × 6 ft | 2400 | 24.0 | 16.0 | 9.6 |
| 300 ft × 6 ft | 3600 | 36.0 | 24.0 | 14.4 |
Preparing and applying
- New wood often needs a few weeks to dry, and a test of water absorption: drops that soak in mean it is ready.
- Old wood should be cleaned of dirt, mildew and loose finish with a wood cleaner or brightener, and rinsed.
- Weather: stain in dry weather between about 50 and 90 °F. Avoid direct hot sun, which dries the surface before it soaks in.
- Method: brushes push the stain into the grain; sprayers are fast but need back-brushing and more product.
- Mix cans of the same colour together in a larger bucket (“boxing”) to keep the tone even.
Choosing a product
Transparent and semi-transparent stains show the grain, but fade sooner; solid stains hide the grain and last longer. Water-based products clean up easily, while oil-based penetrate deeper. Check that the label says it is suitable for vertical surfaces and for the wood species, such as cedar or pressure-treated pine.
For horizontal wood surfaces use the Deck Stain Calculator. To estimate the fence itself see the Fence Calculator or the Vinyl Fence Calculator, and for post footings the Post Hole Concrete Calculator. The Paint Calculator works for painted fences.
Frequently asked questions
How much stain do I need for 100 feet of fence?
A 6 ft tall solid fence 100 ft long is 600 sq ft per side, or 1,200 sq ft for both sides. At 150 sq ft per gallon that is 8 gallons for one coat.
How much does a gallon of fence stain cover?
Manufacturers typically quote 150 to 300 sq ft per gallon on smooth, previously stained wood and less on new, rough or weathered boards, often 100 to 150 sq ft. The label rating for your product is the number to use.
Does a semi-transparent stain need two coats?
Often one coat is enough, because a second coat can fail to penetrate and then peels. Follow the product’s instructions, particularly “wet on wet” rules.
Do I need to count the posts and rails?
The simplest approach is to stain the fence as a plane of boards and add a little extra. Posts and rails add surface, which the 10% extra covers roughly. Increase it for fences with many rails.
How do I calculate an open picket fence?
The style menu reduces the area to the share of the plane that is actually covered by boards. A pressure sprayer wastes more than a brush or roller, so add extra if you spray.