Horse shoes come in various sizes and shapes, varying in terms of:
The shape of front hooves is different than for rear hooves, so one needs to specify not only the size but also whether it is for the front or rear.
Horseshoe Size Chart
When choosing a horse shoe, the first criteria is the size (length and width). Unfortunately, the 'standard sizes' vary somewhat from one manufacturer to another, so one cannot say that a horse needs a given size, without also specifying which manufacturer is providing the horseshoe. To illustrate this, compare the following two charts, the first one being a relatively generic publication.
This second chart, for comparison purposes, is from Epona Shoe. The first thing to note is that for each size they have two variations, narrow and wide, to allow for different shaped hooves. The sizes are also slightly different; for example in the above chart a size 1 has a length of 6 inches, while in the following chart it has a length of 5.5 inches. Comparisons of other suppliers can show even larger differences in standard sizes, in some cases over 1.5 inches difference for the same size. To make matters even more complex, some manufacturers have multiple brands, with different size charts for different brands. Consequently, 'horseshoe size' is only meaningful if one specifies not only the supplier but also the exact brand.
This problem of different horse shoe charts using different values (in some cases, greatly different values) has resulted in a lot of confusion. Some people will say things like 'my horse takes a size 4 horseshoe', whereas in fact the horse takes size 4 of the brand of horseshoe that their farrier happens to be using, but with a different brand the horse may require a size more or a size less ( e.g. a size 3 or size 5). A more accurate approach is to state that the horse requires a horseshoe which is a given number of inches (or millimeters) wide and a given number of inches (or millimeters) long.
To make things even more complex, the required size can be affected by how the horse is being used and the associated shoeing requirements. For example, a horse which is being used for trail may be fitted with a wide and long horseshoe, which extends slightly beyond the hoof, for maximum support but a horse being used for polo will have a very tight fitting shoe (due to risk of other horses milling around stepping on the edge of a protruding horseshoe). Consequently, two horses with exactly the same size hoof may take slightly different sized horseshoes in response to the requirements being placed on the horse and the environment in which it is being used.
Aside from the length and width of the horseshoe itself, there is also the question of the length and width of the metal. In other words, how big the horseshoe's cross-section is. These and other factors are discussed near the bottom of article Horse Shoe Types.
For related articles, click on Horseshoe Information, or on any of the following: