I found this great article on Horse.com that I found pretty helpful. I hope someone else could use the information.

Not all horses need to wear shoes. In fact, some horses experience less hoof-related problems by going barefoot. The only drawback with a barefoot horse is the lack of hoof protection can sometimes lead to injury from hard surfaces, sharp stones, and other hazards. The added support of the boot while out on the trail is why so many horse owners choose to use them.

Choosing a particular style of hoof boot is easy; determining the correct size is another matter. Getting the right measurements are essential to purchasing properly fitting hoof boots. Here is how:

• Try to measure the hooves after a trim for better accuracy.

• Begin by lifting the horse's foot and placing it between your legs. The foot should be positioned so that the bottom of the hoof is facing you. Now that you have easy access to the hoof, clean it out thoroughly with a hoof pick and brush. Caked on dirt can lead to an inaccurate measurement.

• Measure the length of your horse's hoof by placing the tape measure across the middle of the front of the hoof or the toe and stretch it straight back to the middle of the back of the hoof, commonly known as the buttress.

• Determining where the heel buttress line is can be a little tricky for those who have never done it before. The buttress line is the farthest weight bearing point of the heel. Follow the collateral grooves along the sides of the frog which form a V. The hoof wall curves inward towards the bar at this point, which is the heel buttress. Now that you know where the heel buttresses are, imagine a line across the back of the foot and measure from that line to the toe. The heel bulbs are not included in your measurements.

• Find the widest part of the bottom of your horse's hoof and measure at this point.

• Now that you have all your measurements, compare them to our sizing chart. Find the corresponding size in the brand of hoof boot you are interested in.

• It is sometimes recommended that you use a boot one size bigger or you may have difficulty getting the boots on the hoof.

• If you are unsure how to do this yourself, speak with your farrier. He or she will gladly help you measure your horse’s hooves.

There are several different boots and each has its own unique benefits. No matter what boot you choose, measuring the hoof correctly will help allow your horse to comfortably bear its weight and help keep your horse performing its best.