Talk about horsepower, and most of us automatically think about vehicles! But of course, the word horsepower was originally used to describe our equine friends and their sheer power! But how many horsepower does a horse have?
Most people would assume that one horse equals one horsepower, but it isn’t quite as simple as that! Horsepower is calculated as the average amount of work done by one draft horse over a normal working day.
Let’s take a look at the horsepower of a horse, and find out how many horsepower a horse has.
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What Is Horsepower And How Is It Calculated?
Horsepower is a unit of measurement of power. Power is the rate at which work is done – so not just how strong something is, but also how fast the work is carried out.
The term horsepower was originally used to compare the power of steam engines to the power of working horses. The aim was to prove that the newly improved steam engines were more powerful. In the late 18^{th} century, engineer and inventor James Watts came up with a measurement called horsepower. His aim was to convince reluctant customers to invest in his newlyinvented steam engines!
At this time, most of the heavy work was carried out by draft horses. These are large breeds of horses who were bred for strength, not speed. They could work for long hours at a steady pace.
James Watt calculated that a working draft horse could turn a 24ft mill wheel around 2.5 times every minute during an average workday. He then estimated how much force the horse needed to use to turn the wheel, and calculated the overall power of the horse per working day.
It would be pretty rare to find a horse turning a grinding wheel in a mill these days! Modern methods have refined James Watt’s methods, but his calculation was pretty close!
Watt’s original calculation of horsepower was approximately equal to 746 Watts, and the currentday figure is about 735 Watts. Interestingly, it was Mr. Watt who also invented the measurement of Watts!
How Many Horsepower Does A Horse Have?
It would be easy to assume that one horse has one horsepower, but as we’ve already seen, it isn’t that simple! The measurement of horsepower was calculated using the work rate of a draft horse. These are incredibly strong and powerful horses, capable of carrying out heavy work for long periods.
Let’s take a look at the original measurement – a large draft horse turning a millstone around 2.5 times every minute for a full working day. Do you think your favorite horse or pony could handle that workload all day long?
If we put an average modernday horse or pony to work in a mill, it is unlikely that they would be able to sustain a work rate of 1 horsepower for a long period of time. Although all horses are strong and powerful with impressive musculature, they just do not have the sheer bulk of body mass that a draft horse has.
From this, we can conclude that the horsepower of a horse varies according to the size, body weight, muscle mass, and fitness of the horse.
What Is The Average Horsepower Of A Horse?
It is very complex to calculate the average horsepower of a horse, as there are so many variables:
 Size of horse
 Muscle mass
 Bodyweight
 Fitness levels
 Athletic ability
The measurement of horsepower also takes into account the period of time over which the work was carried out. Once you take all these different factors into account, you can see that it is virtually impossible to calculate the average horsepower of a horse. To do this we would need a huge range of different types of horses carrying out the same task, measuring the time taken for each horse.
From this data, we would then be able to calculate the average horsepower of a horse. However, this measurement would only apply to the specific task being analyzed.
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What Is The Maximum HP Of A Horse?
Although it is doubtful that modernday horses can sustain work for long periods like draft horses used to in the mills, they are still immensely powerful creatures. In fact, at peak power production a single horse can exert a considerable amount of horsepower!
Studies have shown that over shorter periods, one single horse can exert up to nearly 15 horsepower. This is because power is a measurement of speed as well as effort/force. As we well know, horses can certainly get up to some impressive speeds!
This means that when we look at the motive (moving) power of a horse, they have up to ten times more horsepower than humans. In fact, horses have more horsepower than all other animal sources of motive power, including oxen, mules, and donkeys.
Fun Facts About Horsepower!
 The world’s strongest horse is Petra, a Belgian Draft Horse. Petra was trained as part of a team to pull logs, and her owner soon realized that this huge horse had impressive levels of horsepower.

A jet engine can create more than 1000 horsepower

The fastest speed record for a horse is held by the mare Winning Brew, who covered two furlongs in under 21 seconds, at a speed of 43.97 mph. That is some serious horsepower!

The most powerful engine in the world can generate an incredible 109000 horsepower. This is enough power to supply an entire suburban town!

One of the world’s smallest breeds of pony, the Shetland Pony, is actually one of the strongest! Poundforpound, this short stocky breed can pull an impressive amount of weight and would outperform the larger draft breeds if it was the same size!
So, as we’ve learned, the horsepower of a horse is the amount of work one draught horse would do over a normal working day. It is unlikely our modernday riding horses are this strong, so our horses are probably less than one horsepower!
We’d love to hear about your horses and ponies, and how much horsepower you think they might have. Please add a comment below!