πͺ΅ Deck Stain Calculator
Calculate gallons of stain needed for decks, fences, and wood surfaces.
Stain Needed
How to Use This Calculator
Enter the surface length and width in feet. Choose the wood condition that matches your project: new smooth wood covers the most per gallon, while weathered and porous old wood soaks up stain quickly and covers less area. Set the number of coats and waste percentage to get your total gallon count.
Measure the surface length and width in feet. For a deck, measure the overall board area, not the structural frame beneath. For a fence, measure total length times height.
Choose the wood condition. New, smooth pressure-treated lumber covers about 250 sq ft per gallon. Weathered gray wood may only cover 100 to 150 sq ft per gallon because the open wood fibers absorb much more product.
Set the number of coats. New wood needs 2 coats. Weathered wood that was stripped to bare wood also needs 2 coats. Previously stained wood in good condition may only need 1 coat as a refresh.
Add 10% waste. You will lose some stain to drips, brush loading, and the spaces between deck boards.
Stain Coverage Formula
A 16x20 ft deck (320 sq ft) at 200 sq ft per gallon with 2 coats needs 3.2 gallons before waste, or 3.5 gallons with 10% waste. You would buy 4 gallons. For a 150-foot fence at 5 feet tall (750 sq ft per side), staining both sides at 150 sq ft per gallon for weathered wood with 2 coats means 10 gallons.
Example Projects
Tips for Your Project
Clean the wood before you stain it. A deck cleaner or oxygen bleach solution removes dirt, mildew, and gray oxidation. Rinse well and let the wood dry for 48 to 72 hours before applying stain. Do not stain wet or damp wood. The stain will not penetrate properly and the finish will peel within one season. Check the moisture content of the wood if you have a moisture meter. Most stain manufacturers recommend below 15% moisture content.
Apply stain in temperatures between 50 and 90 degrees Fahrenheit with no rain forecast for at least 24 to 48 hours after application. Direct, hot sunlight on the wood surface accelerates drying too fast and prevents proper penetration. Early morning or cloudy days are ideal. For deck boards, stain between the boards with a brush before rolling the deck surface to ensure the board edges and sides are covered. Moisture gets into decks primarily from the sides and ends of boards, not the top surface.
Frequently Asked Questions
How much does a gallon of deck stain cover?
New, smooth, unweathered wood: 200β300 sq ft/gallon. Weathered, rough, or porous wood: 100β200 sq ft/gallon. Always check the manufacturer's label.
How many coats of stain do I need?
New wood: 2 coats. Previously stained wood (same stain type): 1β2 coats. Weathered/bare wood: 2 coats. Transparent stains may need more coats for color depth.
Solid vs semi-transparent vs transparent stain?
Transparent: shows grain fully, shortest lifespan (1β2 years). Semi-transparent: shows grain, 2β3 years. Solid: covers wood like paint, 3β5 years.
Should I stain between deck boards?
Yes β stain between boards on the sides. Use a brush or roller applicator designed for gaps. These vertical surfaces need coverage to prevent moisture intrusion.
How long does deck stain last?
Transparent: 1β2 years. Semi-transparent: 2β3 years. Semi-solid: 3β4 years. Solid: 3β5 years. Vertical surfaces last longer than horizontal.