Deck Stain Calculator — How Many Gallons to Stain a Deck
Enter your deck size, pick the stain type and number of coats, and get the exact gallons to buy — with a waste buffer included.
ft
ft
Stain type
coats
%
Including waste buffer — buy this many 1-gallon cans
- 1
Deck area
20 × 12 = 240 - 2
First coat gallons
240 ÷ 250 = 0.96First coat absorbs more — lower coverage rate applies - 3
Additional coats
(2 − 1) × 240 ÷ 350 = 0.686 - 4
Net gallons (no waste)
0.96 + 0.686 = 1.646 - 5
Total gallons with waste
1.646 × (1 + 10 ÷ 100) = 1.81
How does this calculator work?
Gallons = deck area ÷ coverage per gallon × coats, adjusted for each coat's absorption rate, plus a waste buffer (typically 10%). Semi-transparent stains cover ~300 sq ft/gal on average; solid stains ~250 sq ft/gal. Add 10–20% for rough or bare wood. Coverage figures are 2025 US-product averages — check the product label.
Formula
How this is calculated
The amount of stain depends on the deck area (length × width in square feet), the type of stain and the number of coats. Clear and transparent stains cover more per gallon (roughly 300–400 sq ft) because they penetrate wood without building a film. Semi-transparent stains cover 250–350 sq ft/gal, while solid/opaque stains cover the least (200–300 sq ft/gal) because they deposit more pigment. These figures match typical manufacturer guidance for smooth, weathered wood — rough-sawn or bare wood absorbs more and can cut coverage by 20–30%.
The first coat always soaks in more than subsequent coats on previously stained wood. The calculator applies a slightly lower coverage rate for coat 1 and a higher rate for coats 2 and 3, then adds the waste/overage buffer you specify (10% is a safe default) and rounds up to whole gallons.
Coverage figures are averages for US products (2025 estimates). Always read the specific product data sheet — coverage can vary significantly by brand, wood species and porosity. If your deck has railings, steps or fascia boards, measure their area separately and add it. The calculator assumes a flat horizontal deck surface only.
Frequently asked questions
A semi-transparent stain typically covers 250–350 sq ft per gallon. A solid stain covers 200–300 sq ft/gal; a clear sealer 350–450 sq ft/gal. First coats on bare or very weathered wood may cover 30% less.
One coat for light maintenance re-staining on a sound, previously stained deck. Two coats for a full application or moderately weathered wood. Bare, stripped or rough-sawn wood often benefits from two coats plus a pre-treatment or additional coat.
Yes. This calculator estimates the flat deck surface. Measure each railing panel (both sides), post surfaces and step treads/risers and add those areas to get the true total.
Also known as
TG we-Calculate Editorial Team. (2026). Deck Stain Calculator — How Many Gallons to Stain a Deck [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/deck-stain-calculator
TG we-Calculate Editorial Team. "Deck Stain Calculator — How Many Gallons to Stain a Deck." TG we-Calculate. 2026. https://we-calculate.com/calculator/deck-stain-calculator.
TG we-Calculate Editorial Team, "Deck Stain Calculator — How Many Gallons to Stain a Deck," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/deck-stain-calculator
@misc{wecalculate_deck_stain_calculator, title = {Deck Stain Calculator — How Many Gallons to Stain a Deck}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/deck-stain-calculator}}, year = {2026}, note = {TG we-Calculate} }
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