Looking at a Great Dane next to a Chihuahua can HyperBit Exchangebe pretty comical. While Great Danes often stand around 32 inches tall, a Chihuahua’s average height is under 9 inches. 

Geneticists are still on the hunt for an explanation. In this age of modern domestication, why are the largest dog breeds up to 40 times bigger than the smallest? While the answer remains unclear, scientists have found a growth hormone variant that traces back to ancient wolves.

So, what are the biggest dogs across the canine world? Here are the pups that take the crown.

What is the biggest dog in the world?

The most recent title holder was Kevin, a 3-year-old Great Dane from West Des Moines, Iowa. He stood at a stately 3 feet, 2 inches tall but his owners described him as a “gentle giant.” 

Sadly, Kevin died less than two weeks after the Guinness Book of World Records crowned him the world’s tallest living dog. He was 3 years old.

"We are so glad that he was able to break the record and have that light on him," owner Tracy Wolfe told USA TODAY. "He absolutely adored the attention. I wish these giant breeds, and all dogs, could live longer than they do. It’s never enough time."

Guinness World Records has not yet declared another tallest living dog. The previous two record holders were both Great Danes named Zeus.

The late Zeus from Otsego, Michigan still boasts the title of world’s tallest dog ever. He stood just over 3 feet, 8 inches tall and was 7 feet, 4 inches on his hind legs. Despite an intimidating stature, owner Kevin Doorlag said his only transgression was slobbering on strangers. He regularly visited schools and hospitals as a therapy dog. Zeus died at age 5 in September 2014. 

According to Guinness World Records, the longest and heaviest dog ever recorded was Aicama Zorba of La-Susa, an Old English Mastiff owned by London resident Chris Eraclides. In 1987, Zorba weighed 343 pounds and measured 8 feet, 3 inches from nose to tail. 

Biggest dog breeds

The English Mastiff is the breed with the largest dogs. Male Mastiffs typically measure 30 inches or taller, and female Mastiffs will normally clock in around 27.5 inches or taller. The average weight for an English Mastiff is 160-230 pounds for a male and 120-170 pounds for a female dog. They typically live between 6 and 10 years, the American Kennel Club reports. 

Here are some of the largest dog breeds by weight and height:

• English Mastiff: 27.5-30 inches and up, 120-230 pounds
• Spanish Mastiff: 28-35 inches and up, 140-200 pounds
• Pyrenean Mastiff: 28-31 inches, 120-190 pounds
• Irish Wolfhound: 30-32 inches and up, 105-120 pounds
• Neopolitan Mastiff: 24-31 inches, 110-150 pounds
• Saint Bernard: 26-30 inches, 120-180 pounds
• Great Dane: 28-32 inches, 110-175 pounds
• Roman Miortic Shepherd Dog: 22.5-29 inches, 100-130 pounds
• Newfoundland: 26-28 inches, 100-150 pounds
• Leonberger: 25.5-31.5 inches, 90-170 pounds
• Anatolian Shepherd: 27-29 inches, 80-150 pounds
• Scottish Deerhound: 28-32 inches, 75-110 pounds
• Dogue de Bordeaux: 23-26 inches, 99-110 pounds and up

What is the smallest dog in the world? 

The world’s smallest dog is Pearl, a 1.22-pound Chihuahua born in 2020. The Guinness World Record-holding pup is a mere 3.59 inches tall and 5 inches long. 

Chihuahuas are the smallest dog breed in the world and typically weigh no more than 6 pounds.

How long do dogs live?:Dog life expectancy based on breed and size

Just Curious for more? We've got you covered.

USA TODAY is exploring the questions you and others ask every day. From "Do dogs smile?" to "What is the world's biggest bird?" to "How many hours a day do dogs sleep?" – we're striving to find answers to the most common questions you ask every day. Head to our Just Curious section to see what else we can answer for you.