Fence Stain Calculator

How it is calculated

The tool works in feet and square feet. The area of one face is length × height; because both sides are stained it is doubled: A = 2 × L × H. Each coat repeats that area, so total area = A × coats and gallons = total area ÷ coverage, where coverage is the square feet one gallon covers per coat according to the label. The result shows the exact gallons to two decimals, the total area, and a second figure rounded up to whole gallons so you know how much to buy. If the coats field is left empty one coat is assumed; coats of 0 or less, or a coverage of 0 or less, give no result. Only flat fence faces are measured, so extra for rough or weathered boards, posts and gates is not included.

Common mistakes

• Counting only one side of the fence. The tool already doubles the area, so entering a doubled length or height would count the fence four times.
• Entering metres or centimetres. Length and height are read as feet and coverage as square feet per gallon, so metric values give a wrong amount.
• Using the coverage printed for smooth, sealed surfaces on raw or rough wood. Porous boards soak up stain, so the real coverage per gallon is lower than the label figure.
• Forgetting that the coats field multiplies everything. Leaving it empty means one coat, while a label asking for two coats needs a 2 here.
• Buying the exact decimal gallons. The whole-gallon figure is the practical purchase amount, because stain is sold in full containers.