The Greyhound is widely recognized as the fastest dog breed in the world, capable of reaching approximately 40–45 miles per hour (64–72 km/h) in a short sprint under suitable conditions. Its remarkable speed is the result of thousands of years of selective breeding, a lightweight but powerful body, unusually flexible movement, and an extraordinary ability to accelerate.

But the Greyhound’s story is about much more than speed. It is a breed with an ancient history, a specialized hunting background, an impressive athletic design, and a surprisingly calm temperament when it is not running.

Below is a detailed, article-style guide covering its history, speed in numbers, physical characteristics, running mechanics, comparisons with other fast breeds, and the science behind its remarkable performance.

1. The Greyhound in numbers

Greyhound at a glance

Breed profile · American Kennel Club

Top speed

40–45 mph

64–72 km/h, commonly reported estimates

Height at the shoulder

Male: 28–30 in (71–76 cm)

Female: 27–28 in (69–71 cm)

Typical weight

Male: 65–70 lb (29–32 kg)

Female: 60–65 lb (27–29 kg)

Life expectancy

10–13 years

These height, weight, and lifespan figures are published by the American Kennel Club. Speed figures are less standardized because results depend on the dog, course, surface, distance, and measuring method.

What does 45 mph actually mean?

Here is what the Greyhound’s commonly quoted top speed looks like when converted into other units.

Measurement	Equivalent
Miles per hour	45 mph
Kilometres per hour	72.4 km/h
Metres per second	20.1 m/s
Metres travelled in 1 second at that speed	20.1 m
Time to cover 100 m at a constant 45 mph	4.97 seconds
Time to cover 400 m at a constant 45 mph	19.9 seconds

The last two figures are mathematical illustrations, not actual Greyhound race times. A dog must accelerate from the starting line, and its speed changes throughout a run.

An important distinction: the often-quoted 45 mph is a commonly reported upper estimate, not the same thing as a formally timed record. Guinness World Records lists a Greyhound named Star Title at 41.83 mph (67.32 km/h), timed over 366 meters (400 yards) in 19.57 seconds at Australia, on March 5, 1994.

How long can a Greyhound maintain its maximum speed?

This is one of the most important questions when comparing fast dogs.

A Greyhound is primarily a sprinter, not a long-distance runner at maximum speed. Its peak velocity is achieved during a short, intense effort. It cannot maintain 45 mph for an entire race.

Historical Greyhound breed information from Grey save reports that Greyhounds can average more than 30 mph over distances up to one mile. That should be treated as a general breed-performance claim rather than a guaranteed pace for every dog or race.

There are three different measurements worth distinguishing:

• Peak speed: the fastest instantaneous speed reached during a run.
• Average speed: total distance divided by total elapsed time, including acceleration.
• Endurance: how well the dog sustains a pace over a longer distance.

A dog can have an extraordinary peak speed without being the best endurance runner. That is why a Greyhound’s maximum speed should not be confused with the ability to sustain that speed over several minutes.