Deck · updated 2026
Deck Stain Calculator
A deck floor is the harshest surface stain can face — full sun, standing water, foot traffic — so the right amount applied correctly matters more than the brand. This deck stain calculator converts your deck’s square footage (floor only, or floor plus railings) into exact gallons for your chosen number of coats at real coverage rates, plus 2026 stain costs. Railings roughly double the surface area, which is why there is a toggle instead of a guess.
Railings add roughly 50% more surface area
Most deck stains cover 150–300 sq ft/gal; use 150 for rough or weathered wood
Show the math
Floor area = 16 × 12 = 192.0 sq ft
Surface area = 192.0 × 1.50 (railings both sides) = 288.0 sq ft
Gallons = 288.0 × 2 coat(s) ÷ 200.0 sq ft/gal = 2.88 gal
Cost = 2.88 gal × $40–$60/gal
What the numbers mean
The calculator converts your measurements into a practical purchase quantity using a documented coverage or spacing assumption.
Any whole-unit quantity is rounded up so the result does not leave you short during the project.
Use the cost range as a planning baseline and confirm the final quantity, availability, and delivery charge with your local supplier.
2026 material prices
| Material | 2026 average price | Note |
|---|---|---|
| Deck stain, per gallon | $40.00 – $60.00 / gallon | Semi-transparent, retail |
| Deck cleaner/brightener | $15.00 – $25.00 / gallon | Per gallon, for prep |
Material prices: Phase 2 2026 national-average guide, Sep 2026. Local prices vary. 2026 U.S. national averages. Prices vary by region and retailer — confirm locally before buying.
Pro tips
- Prep is 80% of the job — clean and brighten first, or the stain fails in a year regardless of brand.
- Stain the railings and undersides first, floor last, so drips land on unstained wood.
- Work in the shade or on overcast days; hot sun dries stain before it penetrates.
- Two thin coats beat one thick coat — thick stain films peel like paint.
- A 16×12 deck with railings needs about 3 gallons for two coats — buy it all at once for color consistency.
- Restain horizontal surfaces every 2–3 years; vertical railings and skirting last 3–4.
Common questions
Frequently asked questions
How much stain for a 16×12 deck?
Floor only: 192 sq ft × 2 coats ÷ 200 = 1.9 gallons (buy 2). With railings: about 2.9 gallons (buy 3).
How many square feet does a gallon of deck stain cover?
150–300 sq ft per gallon — 200 is typical; use 150 for rough or badly weathered wood.
How often should I stain my deck?
Every 2–3 years for the floor; railings and vertical surfaces every 3–4.
Semi-transparent vs solid stain?
Semi-transparent shows the grain and lasts 2–3 years; solid lasts 4–5 but hides the wood completely.
When is the best time to stain a deck?
Spring or fall, 50–90°F, with 24–48 hours of dry weather after application.
Do I need to strip old stain first?
If it is peeling or flaking, yes — strip it. If it is just faded, a cleaner and brightener is enough prep.
Related calculators
Planning estimates only. Prices are 2026 U.S. national averages and vary by region — confirm with your local supplier before buying.