Mythbuster Monday: The Final Height of a Horse Can Be Determined When It’s a Yearling

On Mythbuster Monday, we tackle a variety of equestrian myths to either bust or confirm. Today’s discussion: Can you tell how tall a horse is going to be when he is a yearling?

It’s Mythbuster Monday, where Horse Nation dives into different equestrian myths and provides research-based evidence to either bust or confirm those myths. Today’s topic: Can you tell how tall a horse is going to be when he is a yearling? What is the rule to determine height? Where did this information first originate? Read further to find out!

Myth: You can tell how tall a horse is going to be when he is a yearling

Myth or Fact: Myth


A yearling is a young horse of either sex that is between one and two years old. Many horse people believe you can judge how tall your horse will be at this age by using a measuring tape to measure from the ergot to the wither and add one inch. Then convert that measurement to hands (four inches equal one hand). Divide your measurement in inches by 4 and that will equal your horse’s mature height. But, can you really tell how tall your horse is going to be while he’s still a yearling?


According to an article published by Horse Lover’s Math, this method is accurate because a horse’s legs are to maturity by the time they hit the two-year-old mark. However, this was the only article we found asserting this and they didn’t state much more.


Malgre Tout Media disagrees with this statement in their article. They write that the healthy growth of a young horse is on a curve. There are many factors to consider, such as feeding regimen, which can alter the pace a horse will grow. They also state that different breeds of horses have different growth rates. Although there are methods that can be used to get a rough estimate as to how tall the horse will be full grown, there’s no way to be exact.


Fédération Equestre Internationale (FEI) states in their article that some methods to measure full grown height in a yearling are more accurate than others. The article discusses research that indicates foals have reached nearly three quarters of their mature height by 3 months old, by six months old, they’re over 80% of their mature height, and by the time they’ve reached two years old, they’re nearly done growing. Studies have shown that cannon and pastern bone measurements increase less than 7% from weaning age right up until the horse is three. This indicates that the lower limbs are just about finished developing by the time a horse has reached one year old, meaning they are a great tool to estimate mature height.

Regardless of the timeline provided by science, FEI states the methods to calculate final height are not 100% accurate.  There is too much potential for variance. The only way to know what height a horse will be when he’s full grown is to wait to see the height he becomes when fully developed.


After diving into the research, it’s important to note that using the yearling trick to determine full grown height is just a guideline. There are factors that can make horses develop faster or slower than the suggestions. However, using the age-old trick is a good way to get a rough estimate when determining the height of your new partner.

Do you have an equine myth you’d like us to tackle? If so, send it our way! Email your suggestions to [email protected]. Put Mythbuster Monday in your subject line.