How To Determine Coverage Rates for Coating Projects

Before applying a protective coating, the most important thing to consider is how much material you will need. Knowing this amount will also help you determine the potential cost of a coating project. There are four main factors you will need to consider to determine this:

• How big is the area you need to cover / how big is the project?
  • The area is typically determined by calculating square footage (length x width).
  • If you are working with a rougher surface, you may need more coating.
• How are you applying the coating?
  • Spraying versus rolling or brushing the coating onto the surface can affect how much material you need. Rolling and brushing techniques usually require more coating due to waste generated during the mixing, pouring, and application process.
• How thick do you need the coating to be for optimal protection?
  • All coatings vary in terms of thickness requirements. These requirements can be found on the technical data sheet. There is a minimum amount recommended to create uniform coverage that will protect the surface or project. The thicker you apply the coating, the more you’ll need.
• What is the solids content of the coating?
  • Solids content is the amount of potential solvents in a coating that will evaporate while it cures. So, the wet film thickness will differ from the dry film thickness.
  • For coatings that are 100% solids, you don’t have to worry about volatile content or low solids content affecting the dry film thickness. In other words, the amount you apply is the amount that will remain on the surface. Most of VFI’s industrial coatings and hard coats have a 100% solids content, so this is not a concern when determining the material needed.

Why Coating Thickness Is Important & How to Measure

Coating thickness directly affects the durability and performance of the coating. Ensuring you apply enough material will allow the coating to provide an effective protective barrier. Coatings like urethanes, polyureas, and hybrids can provide resistance to corrosion, weathering, abrasion, and chemicals.

Most manufacturers list coating thickness in mils. Some applicators might be unfamiliar with the term. A mil is defined as one-thousandth of an inch. Coating thickness is expressed this way because these materials are applied thin (under a quarter of an inch or 250 mils). Film thickness can be measured before the coating has cured with a mil gauge.

One gallon of a 100% solids coating applied at one mil will cover 1604 square feet. Knowing how many square feet a single mil covers can aid in the process of determining how many gallons you need to cover a specific area at a specific mil thickness. Knowing the coating thickness helps you control costs while ensuring adequate coverage.

All VFI coatings specify thickness requirements on each technical data sheet. Follow these specifications to create a durable layer with good physical properties to protect various surfaces. You will also need to know your desired mil thickness to help calculate how much material you will need.

What Happens with Improper Coating Thickness?

If you are not applying the recommended amount of a coating as specified by the manufacturer, it can affect several properties and the material’s ability to form a proper protective surface. Following the manufacturer’s instructions can help you avoid various issues, including coating failure. The application should be consistent and uniform across the entire surface for the best results.

Inadequate coating application can result in:

• Property Reduction – A thinner coating may not be able to reach its full properties and will affect the cure speed.
• Adhesion issues – The coating needs to be applied thick enough to develop a bond with the surface. If the bond fails, the coating might peel, crack, or delaminate over time.
• Surface defects – Insufficient coating thickness can create small voids or pinholes on the surface.
• Project delays – If you run out of material before you’re finished with the application, needing to get more will cause delays.

Excessive coating application can result in:

• Sagging – Applying a lot of material, especially over vertical surfaces, can cause sagging. The coating will settle unevenly and be thicker in certain spots.
• Cracking – If the coating is too thick, temperature fluctuations or stress can make it more prone to cracking.
• Shorter cure – The cure time of most coatings is tested at a standard mil thickness. Excessively applying the coating can shorten the cure time, resulting in reduced recoat window and adhesion issues.
• Material waste – If you apply more material than you truly need, you’re wasting material you could use for a different project and increasing expenses.

How to Calculate Coating Coverage

When calculating the material you need, it will be an estimate, as various factors could affect the actual amount required. You’ll first need to know the surface area you need to cover. We recommend finding the square footage, which can be determined through the simple math formula length x width.

• Formula: L x W = Area (Square Footage)

The most common formula used to calculate the application rate per gallon is dividing the square footage per gallon of a single mil by the desired dry mil thickness.

• Formula: 1604 sq. ft. per gallon / desired mil thickness = coverage (sq. ft.) per gallon

Ex.) A manufacturer requires a coating to be applied at a minimum mil thickness of 40. To determine how many square feet the coating would cover at this thickness, you would use the following equation:

• 1604 sq. ft. per gallon / 40 dry mils = 40.1 sq. ft. per gallon

Now, let’s say you determined that you have 100 square feet (10 ft x 10 ft) to cover at 40 dry mils. You would divide the project square footage by the square footage the desired mil thickness covers to get the minimum number of gallons required.

• 100 sq. ft. per gallon / 40.1 sq. ft. per gallon = 2.49 gallons

You would then round that to a whole number (3 gallons). Because VFI’s coatings come in 1-gallon kits, 5-gallon kits, drums, or totes, we’d recommend a 5-gallon kit of material for this project to account for potential waste.

Accounting for Waste

An estimate does not account for surface texture, overspray, spills, equipment problems, or application methods. It’s always a good idea to add 10-15% of material to your calculations to account for shortages that would otherwise cost you time and money.

Coating Coverage Chart by Mil Recommendations

VFI typically does not recommend using any of our coatings, whether that be industrial coatings, bedliners, or hard coats, under 30 mils. Please read the technical data sheet associated with the product for thickness requirements before application.

Mil Thickness	Coverage (Sq. ft. per Gallon)
1	1604
30	53.46
40	40.1
50	32.08
60	26.73
70	22.9
80	20.05
90	17.82
100	16.04
110	14.58
120	13.36
250	6.41

Contact VFI if you have more questions about coating application or thickness requirements.