Use this calculator to figure mil thickness of coatings.

Demystifying Mil Thickness: Getting Your Concrete Floor Coating Right Every Time

If you’ve spent any time around epoxy, polyaspartic, or urethane floor coatings, you’ve probably heard the term "mil thickness" thrown around. But what exactly is a "mil," and why does it matter so much for your bottom line and the success of your project?

At Concrete Floor Supply, we know that hitting the right application rate is the difference between a floor that lasts for decades and a call-back a few months later. Here is a simple breakdown of how mil thickness works and how to make sure you are applying your products correctly every single time.

What is a "Mil"?

A "mil" is simply a unit of measurement equal to one-thousandth of an inch (0.001 inches). To give you a visual:

• A standard piece of printer paper is about 4 mils thick.

• A standard credit card is roughly 30 mils thick.

When we talk about floor coatings, we measure how thick the liquid is applied (Wet Film Thickness) and how thick it is once fully cured (Dry Film Thickness) in mils.

Why Mil Thickness Matters

Hitting the manufacturer’s recommended mil thickness isn't just a suggestion—it's a critical requirement for the performance of the floor.

• Applying Too Thin: The coating won't have the physical strength to withstand vehicle traffic, chemicals, or impact. It can also lead to roller marks, an uneven finish, or poor hiding of the concrete profile below.

• Applying Too Thick: You are literally pouring your profit down the drain by wasting expensive material. Worse, applying a coating too thick can trap solvents or moisture, leading to curing issues, bubbling, or a soft floor that easily scratches.

The Magic Number: 1600

To figure out your coverage, you need to know the universal rule of thumb in the coatings industry: One gallon of a 100% solids coating will cover 1,600 square feet at exactly 1 mil thick.

Using that baseline, if you want a 10-mil thick floor, you divide 1,600 by 10. That means one gallon will cover 160 square feet.

The Factor of "% Solids"

The math gets a little trickier because not all products are 100% solids. Many water-based or solvent-based epoxies and urethanes have a lower solids percentage—meaning some of the liquid will evaporate into the air as it cures.

If a product is 50% solids, half of it evaporates. That means you need to apply it twice as thick while wet to get the same dry mil thickness as a 100% solids product.

Taking the Guesswork Out

Doing the math on the fly can be a headache, especially when you are mixing batches and the clock is ticking on your pot life. That’s exactly why we provide our Mil Thickness and Coverage Chart and our interactive calculator.

Before you start pouring:

1. Check the % Solids on the technical data sheet for the product you are using.

2. Determine your target Spread Rate (Square Feet per Gallon).

3. Use our chart or calculator to instantly verify your applied Mil Thickness.

Getting your coverage rates dialed in protects your reputation and helps you better understand the proper application rates.  Our data sheets will always tell you how many sqft/gallon you should be applying a particular product. Always read tech data sheets.  If you have any questions about the right application rates or products for your specific project, the team at Concrete Floor Supply is always here to help.