How this calculator works
Projected area times faces, exposed-surface factor and coats gives coating demand. Divide by coverage and add an allowance for application losses. Round only the purchase quantity to whole cans. A box or board-on-board fence can expose more wood than its simple outline; use actual area or an appropriate measured factor.
Formula
required volume = one-side area x sides x surface factor x coats x (1+loss) / coverage; cans = ceil(required volume/can volume); cost = cans x price.
Worked example
A 20 m by 1.8 m fence stained on both faces for two coats at 10 m^2/L needs 14.4 L before losses, or 15.84 L with 10% allowance.
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Frequently asked questions
Should transparent stain always get one coat?
Follow the product label. Coat count is an input because products and substrates differ.
Do picket gaps reduce the painted area?
Yes, while edges and rails add area. Enter measured exposed area or adjust the surface factor for the actual fence.
Are US and imperial gallons interchangeable?
No. The coverage option specifically uses US gallons. Volume selectors distinguish US and UK imperial gallons.