Ready Seal Stain Calculator: How Much to Buy

The Ready Seal stain calculator helps you estimate how many gallons of Ready Seal wood stain you need for a deck, fence, or other wood surface. You enter the total square footage of the wood and the number of coats you plan to apply; the calculator returns the required gallons based on Ready Seal’s stated coverage rate of 200–250 square feet per gallon per coat.

Formula

The basic formula is:

Gallons needed = (Surface area in ft² ÷ 225) × Number of coats

Where:

• Surface area is the total wood area you will stain, in square feet (ft²).
• 225 is the midpoint of Ready Seal’s stated coverage range (200–250 ft² per gallon per coat). Using the midpoint gives a small safety margin against underestimating.
• Number of coats is how many layers you plan to apply. Ready Seal is typically a one-coat stain, but a second coat may be used on very dry or porous wood.

For metric users: 1 gallon ≈ 3.785 liters. So the same formula can be expressed as Liters = (m² × 10.764 ÷ 225) × coats × 3.785, or simply multiply the gallon result by 3.785.

Worked Example

Using the default values from the calculator (500 ft², 1 coat):

1. Divide the area by the coverage rate: 500 ÷ 225 = 2.222…
2. Multiply by the number of coats: 2.222 × 1 = 2.222
3. Round to two decimal places: 2.22 gallons

In liters: 2.22 × 3.78541 = 8.41 liters.

Since stain is sold in whole gallons, you would need to buy 3 gallons for this project. The calculator shows the fractional amount so you can decide whether to buy a partial gallon (if available) or round up.

Measuring Your Wood Surface Area

Accurate area measurement is the most important step. For a deck, measure the length and width of the deck surface in feet and multiply them. But that only gives you the top of the boards—if you are staining the sides of the boards (the “skirt� or fascia), you need to add those areas separately.

For a fence, measure the height and length of each section. If the fence has gaps between pickets, you can still use the full width—the stain will cover the edges and the back side partially. For a solid privacy fence, measure both sides if you plan to stain both.

Here are common area calculations:

• Deck floor: length × width (e.g., 20 ft × 25 ft = 500 ft²)
• Deck railing: measure the linear feet of railing and multiply by the height (e.g., 40 ft of railing × 3 ft high = 120 ft²)
• Fence (one side): length × height (e.g., 100 ft × 6 ft = 600 ft²)
• Wood siding: measure the wall area and subtract windows and doors (e.g., 800 ft² wall – 100 ft² openings = 700 ft²)

If your wood has a rough surface (like cedar or rough-sawn lumber), it will absorb more stain. In that case, use the lower end of the coverage range (200 ft² per gallon) in your calculation. For smooth, previously stained wood, you can use the higher end (250 ft² per gallon). The calculator uses 225 as a default, but you can adjust the area input up or down to reflect your wood’s porosity.

How Ready Seal Coverage Works

Ready Seal is a penetrating oil-based stain, not a film-forming paint. It soaks into the wood rather than sitting on top. This means coverage depends heavily on the wood’s porosity and moisture content. Dry, weathered wood will absorb more stain than new, milled wood.

The manufacturer states that one gallon covers 200–250 square feet per coat. In practice, many users report getting closer to 200 ft² on rough cedar and 250 ft² on smooth pressure-treated pine. The stain is designed to be applied in one heavy coat—unlike some stains that require two thin coats. If you apply a second coat, it will mainly be absorbed by the most porous areas, so it won’t double the coverage needed. However, for the calculator, we treat each coat as requiring the full coverage amount, which is a safe overestimate.

Ready Seal is also self-priming and can be applied to damp wood (though not wet). This is unusual for stains and can affect how much you need—if the wood is damp, it will absorb less, so your coverage might be better than expected.

Common Mistakes and How to Avoid Them

People often make these errors when estimating stain:

• Forgetting to measure both sides of a fence: If you stain both sides, double the area.
• Using the wrong coverage rate: Ready Seal’s rate is per coat. If you apply two coats, you need double the stain.
• Not accounting for waste: Some stain will be left in the brush or roller, and you may spill a little. Add 5–10% to your total.
• Rounding down: Always round up to the nearest whole gallon. Buying a partial gallon is rarely possible, and you can return unopened cans.
• Mixing units: If you measure in meters, convert to feet before using the formula (1 m² = 10.764 ft²).

One common misconception is that a second coat will make the color darker. Ready Seal is a semi-transparent stain, so the color comes from the pigment in the oil. A second coat may deepen the color slightly on very porous wood, but it won’t change the hue dramatically. If you want a darker color, you need to choose a darker Ready Seal color, not add more coats.

Buying the Right Amount

Ready Seal is sold in 1-gallon, 5-gallon, and 55-gallon containers. For most residential projects, 1 or 5 gallons is practical. Here’s how to decide:

• Under 200 ft²: 1 gallon should be enough for one coat.
• 200–500 ft²: 2–3 gallons for one coat.
• 500–1,000 ft²: 3–5 gallons for one coat.
• Over 1,000 ft²: Consider a 5-gallon pail, which is usually more economical per gallon.

If your calculation gives a number like 2.2 gallons, buy 3 gallons. You can always return unopened cans, but running out mid-project is a hassle. Also, if you are staining a new deck, consider buying a little extra for touch-ups later.

Application Tips That Affect Coverage

How you apply the stain can change how much you need. Here are the key factors:

• Method: Spraying uses less stain than brushing or rolling because less is left in the applicator. However, spraying requires back-brushing to work the stain into the wood, which can increase absorption.
• Temperature: On hot, sunny days, the stain evaporates faster, so you may need more to achieve the same coverage. Apply in the morning or evening when it’s cooler.
• Wood moisture: Ready Seal can be applied to damp wood, but if the wood is very dry, it will soak up more stain. If you’re staining old, dry wood, expect to use the lower coverage rate (200 ft²/gal).
• Knots and grain: Wood with heavy grain or knots will absorb more stain. You may need to apply extra to those areas.

One tip: before you start, test a small area to see how much stain the wood absorbs. This will help you adjust your coverage estimate before you buy all the stain.

Frequently Asked Questions

Can I use this calculator for other stains?

Yes, but you need to adjust the coverage rate. Most stains cover 200–400 ft² per gallon, so check the label. The formula is the same: area ÷ coverage × coats.

Does Ready Seal really cover 250 sq ft per gallon?

The manufacturer states 200–250 ft² per gallon per coat. Actual coverage depends on wood porosity, application method, and weather. For a safe estimate, use 225 ft² per gallon, which is what this calculator uses.

How many coats of Ready Seal should I apply?

Ready Seal is designed as a one-coat stain. A second coat is only needed if the first coat didn’t fully penetrate, which can happen on very dry or rough wood. Applying more than two coats is wasteful and may leave a sticky residue.

Can I apply Ready Seal over old stain?

Yes, Ready Seal can be applied over previously stained or sealed wood as long as the old coating is clean and not peeling. However, the old finish may reduce absorption, so you might need less stain than the calculator suggests.

What if my deck is not a perfect rectangle?

Break the deck into rectangular sections, calculate each area, and add them together. For triangular or curved areas, use approximate measurements. The calculator works with any total area you enter.

Is Ready Seal safe for vegetable gardens?

Ready Seal is an oil-based stain and should not be used on surfaces that come into direct contact with food. If you’re staining a planter box, line it with plastic or use a food-safe sealer instead.

Related

• Fence Estimates Calculator by Type
• Fence Calculator Home Depot: How to Estimate Materials
• Feather Edge Board Calculator: How Many You Need

in sqft | Wood surface area | ft² | 500 | 0 | 100000
in coats | Number of coats | - | 1 | 1 | 3
out gal | Stain needed | gal | sqft / 225 * coats | 2
out liters | Stain needed | L | sqft / 225 * coats * 3.78541 | 2