Garage floor coverings come in different sizes that depend on what kind of covering they are. For example, roll out covers usually have bigger sizes than the average person needs, so you can adjust them exactly the way you want. If you want to use interlocking garage floor covering, then you will know the sizes for each tile. You will have to calculate exactly how many tiles you need and what size.
Ribbed garage floor covering usually comes in four sizes, that are most likely all you need: 7-1/2″x17′, 7-1/2″x20′, 9′x20′ or 10′x22′. Its thickness is designed to protect your concrete better (usually around 0.055″ thick).
Roll out floor covering can have many different sizes. BLT coverings are the best example here. They use the most common types of sizes that anyone could need. First of all, BLT coverings are made in three different thickness grades: 0.055″ is the base thickness and it is called standard grade. It is the most common thickness; 0.075″ is the medium thickness and its name is commercial grade; the thickest of them all is 0.085″ and its name is industrial grade. Enough about the thickness, now it is time to talk about the width and length. The width available for roll out coverings is 7.5′, 8′, 9′, 10′. As for the length you can order a custom length, but the maximum width still is 10′.
The coin patterned garage floor cover from BLT has a 75 mil thickness. You can imagine that as it would be about 18 sheets of copy paper. The size available is 8×22. Other coin patterned garage floor coverings come in sizes as it follows: The standard sizes for them are 7.5×17, 8×22, 9×44, 9×60, 10×24. Except the 9×44 size that comes with 85 mil thickness, all the other ones are 75 mil thick. And here are some other very popular custom sizes that are being used: 7.5×14, 7.5×20, 7.5×22, 9×20, 10×22.
In conclusion, all types of garage floor coverings are designed to be made in all the sizes anyone could need. Coverings can also be made at custom size, but it is usually better and cheaper to buy a standard sized one and cut it to fit perfectly in your garage.