How Tall Will Your Horse Get?

When you’re looking at a foal, yearling, or young horse, it can be hard to picture what they’ll look like once they’re fully grown. One of the biggest questions is usually pretty simple: How tall is this horse actually going to get?

There is no way to predict a young horse’s mature height with complete certainty, but there are a few methods that can give you a pretty good estimate. One of the most common is the string test.

Why the String Test Works

Young horses do a surprising amount of their vertical growing early in life.

According to the FEI, foals have already reached nearly three quarters of their mature height by around three months old. By six months, they are over 80 percent of their mature height, and by two years old, most horses are getting fairly close to their final height.

The lower portion of the leg develops particularly early. Research referenced by the FEI found that cannon and pastern measurements increase by less than 7 percent between weaning and three years old. That relatively stable leg length is what makes measurements taken on a young horse useful for estimating mature height.

How to Do the String Test

The traditional string test is simple and only requires a piece of string or a measuring tape.

Measure from the ground up to the horse’s elbow.

Using a piece of string, hold one end at the horse’s elbow and extend the string down to the ground. Keep your finger on the point of the string that reaches the elbow.

Then, while keeping that point at the elbow, rotate the string upward 180 degrees.

The opposite end of the string will give you an approximate idea of where the horse’s withers may eventually reach.

You can also measure the distance from the ground to the elbow and simply double that measurement to estimate mature height.

For example, if the measurement from the ground to the elbow is approximately 30 inches:

30 inches × 2 = 60 inches

Since one hand equals four inches:

60 inches ÷ 4 = 15 hands

That horse would be estimated to mature around 15 hands tall.

Another Method: Coronet to Knee

There is another common method that uses the lower leg.

Measure from the coronary band to the middle of the knee joint in inches.

Then multiply that measurement by four.

For example:

15 inches × 4 = 60 inches

That works out to approximately 15 hands at maturity.

What About Yearlings and Two Year Olds?

There is also a much simpler rule of thumb sometimes used when estimating height.

For a yearling, you may hear people estimate the mature height by adding approximately two hands to the horse’s current height.

For a two year old, the rough estimate is to add approximately one hand.

This is a much less precise method and should really only be considered a ballpark estimate.

The String Test Is an Estimate, Not a Guarantee

Growth rates vary from horse to horse.

Breed, genetics, nutrition, overall development, and individual growth patterns can all affect the final result. Some breeds also mature more slowly than others.

A horse can continue filling out and changing dramatically after it has reached most of its mature height. A narrow, leggy two year old may look like an entirely different horse at five even if the actual measurement at the withers has changed very little.

That is why the string test is best used to estimate a range, rather than expecting it to predict an exact final measurement.

If the test suggests a youngster will mature around 15.1 hands, it is reasonable to think the horse may finish somewhere around that mark. It would be less reasonable to assume the horse is guaranteed to finish at exactly 15.1.

A Helpful Tool When Shopping for a Young Horse

If you’re considering buying a foal or young horse, the string test can give you another piece of information to work with.

Look at the horse’s current height, the size of its sire and dam, its breed and family, its age, and its overall development along with the string test.

None of those factors can guarantee exactly where a young horse will finish, but together they can give you a much better idea of what that youngster may look like a few years down the road.

And sometimes that little yearling standing in front of you has a lot more growing left to do than you think.

Information for this article was referenced from the Fédération Equestre Internationale’s guide, “How Big Will Your Foal or Youngster Get?”