How much does a racehorse weigh?

The average weight of a racehorse ranges from 1037 pounds (470 kg) to 1985 pounds (900 kg). However, these animals tend to lose 5% of their body weight in a single competition.

This significant weight variation—sometimes exceeding 800 pounds—depends on factors like breed, age, and gender, which result in some horses being larger or smaller than others. Therefore, based on these factors, the horse’s weight can affect its speed, stamina, and overall performance.

Factors that influence a racehorse’s weight

As we said before, there are certain elements at play when talking about a racehorse’s weight. Two of the most important are breed and age. We explain these in detail below:

1. Breed

Now that we have a global understanding of a racehorse’s weight, we must determine the particular weights of the different breeds. This can provide us with useful data about their physical attributes and abilities in each competition.

Each breed has its own unique set of characteristics that contribute to its weight range:

2. Age

Age is a determining factor when it comes to a horse’s weight. There are three stages of growth: birth, foal adolescent, and adult. Let’s take a look at important information about weight at each stage:

1. At birth: the initial weight of a foal at birth is between 99 and 121 pounds (between 45 and 55 kg). But, this obviously varies with the breed. So, to know the ideal weight of a newborn foal, it must be calculated on the basis that it should be 7% of the mother or mare’s weight. It also represents the equivalent of 10% of the weight it will reach as an adult.
2. Young or adolescent foals and colts: in this adolescent stage, horses go through a phase of more rapid growth since they were in the mother’s womb. This is why they appear ungainly, sometimes increasing height and body mass disproportionately. But this is normal. However, it is crucial to monitor their feeding and physical activity during this period to ensure that their growth is healthy. Overfeeding should be avoided, as excessive weight gain in these years can lead to bone disorders and other health difficulties.
3. Adult horses: as horses become adults and age, their metabolism slows, and they require weight regulation for good health. Depending on breed and age, they may require modifications to their diet and physical activity programmes to maintain a healthy body and a balanced weight.

Other factors that can influence a racehorse’s weight

• Gender plays a role, as male horses, especially stallions, tend to weigh more than mares or geldings due to greater muscle mass.
• Diet and nutrition. A balanced diet rich in nutrients helps maintain an optimal weight, while overfeeding or underfeeding can cause fluctuations.
• Training regimens impact weight since intense training builds muscle, increasing weight, while overtraining or dehydration may result in weight loss.
• A horse’s health status is also important because illnesses, parasites, or injuries can affect appetite and metabolism, leading to changes in weight.
• Seasonal changes influence weight, as horses may gain fat for insulation in colder months or lose weight due to heat stress and increased activity in warmer seasons.
• Genetics also play a key role, determining a horse’s natural build and its ability to maintain a specific weight range.

What are the regulations regarding racehorse weight?

In the UK, racehorse weight regulations are set by the British Horseracing Authority (BHA) and vary based on the type of race and the horse’s age and gender. While there is no strict “mandatory” weight for every horse, there are some important guidelines:

• Racehorse weight monitoring: the BHA requires racehorses to be weighed regularly to ensure that their weight is within a suitable range for their performance and well-being. Horses that are too heavy may be at a disadvantage, as extra weight can affect speed and stamina, while horses that are too light may be more prone to injury or fatigue.
• Carrying capacity: it is known that a horse has the capacity to carry between 15 and 20% of its body weight. This obviously includes the rider and any equipment. However, according to UK law, a horse can legally carry only 10% of its body weight in any race or equestrian event, without distinction.

How to measure a horse’s weight

Measuring a horse’s weight is important for its health and performance. While traditional scales aren’t always available, there are simple methods to estimate its weight accurately. Here’s how to do it:

• Tape measure: wrap the tape around the horse’s girth, precisely behind the elbow, and calculate the weight derived. The tape must be correctly adjusted, and the horse must have exhaled. The accuracy of the measurement is based on breed, age, wither dimension and user.
• Electronic scales are the most accurate, quickest and easiest method of calculating the weight of a racehorse. These devices are millimetrically calibrated for this purpose.
• Mathematical formula: it is possible to calculate the weight of a racehorse using this formula:

Weight (Kg) = [ (PT)2 x L ] ÷ 11,000

PT : refers to the thorax perimeter.

L : is the length of the equine. For them, it is measured from the point of the shoulder to the ground.

11.000: is a mathematical constant.

Safety recommendations when weighing a racehorse

✅ Always check that the horse is calm, upright and not tied, saddled or harnessed.

✅ If a tape measure is to be used, it should not be excessively tight around the girth.

✅ If an electronic scale is used, it must be calibrated, its platform must be properly straight and there must be no objects or debris on it. It is advisable to use one of the latest generation and of a good, recognised brand.

✅ It is preferable to have professional help if the measurement is to be done at home or in the stables.