Deck Painting & Staining Cost Calculator
Two answers in one: how much stain to buy and what it costs. Enter your deck’s length and width, the coats and coverage, and your price per square foot — deck area is length × width, gallons round up.
A 16 × 20 ft deck is 320 sq ft — about 3 gallons of stain and about $704.00. Deck boards are thirsty and weather-exposed — semi-transparent stain covers ~200–300 sq ft/gal, and the rails and steps add area; this is painting/staining an existing deck, not building one.
Calculator inputs
A deck job has two questions that people usually answer separately and get wrong together: how much stain do I need, and what will it cost. Both start from the same number — the deck floor area, length × width — so this tool computes them side by side. Buy too little stain and you are chasing a second batch (and a possible color mismatch); buy blind and you overpay.
Deck boards are thirsty and weather-exposed, so coverage runs low — semi-transparent stain typically lays down at ~200–300 sq ft/gal, less on rough or bare wood. The rails, stairs and fascia add real area, so add them to the width side if you are coating them. Gallons always round up to whole cans. To size just the material, cross-check with the paint coverage calculator.
Formula
Area first, then gallons and cost:
deck_area = length_ft × width_ft
gallons = ceil(deck_area × coats ÷ coverage_per_gallon)
cost = (deck_area × $/sq ft + add‑ons) × (1 + contingency%)
- coverage — ~200–300 sq ft/gal for semi-transparent stain; drop it for rough/bare wood.
- gallons — rounded up to whole cans, and buy from one batch for color consistency.
- add-ons — stripping, sanding, rail and stair detail.
Worked example
A 16 × 20 ft deck, 2 coats, stain at 250 sq ft/gal, priced at $2.00 a square foot with 10% contingency:
area = 16 × 20 = 320 sq ft
gallons = ceil(320 × 2 ÷ 250) = ceil(2.56) = 3 gallons
cost = (320 × $2.00) × 1.10 = $640 × 1.10 = $704
So about 3 gallons of stain and roughly $704. Add the rails and steps and both numbers climb — that area is easy to forget and easy to run short on.
Measure first, avoid re-orders
Measure the deck, then add the extras. The floor is length × width; rails, balusters, stairs and fascia are real surface that drinks stain. Fold them into the width dimension or the add-ons rather than pretending they are free.
- Confirm coverage on the can. Semi-transparent, solid and oil stains all spread differently; rough or weathered boards soak up more. Read the stated spread rate and round gallons up.
- Prep drives lifespan. A failing finish needs stripping or sanding first — that is an add-on, and skipping it wastes the stain.
- This coats a deck, it does not build one. Framing, joists and boards are a construction job, not a paint estimate.
- Weather matters. Stain wants dry wood and a dry window — plan the job around it, not the other way around.
Reference table
Labeled coverage (spread rate) — thirsty, weathered or bare wood covers less. Confirm the stated spread rate on the can and round gallons up.
| Surface | Coverage (sq ft/gal) |
|---|---|
| Deck / fence (semi-transparent stain) | 200–300 |
| Bare / rough wood | 200–300 |
| Smooth wood / trim (enamel) | 350–400 |