A dog is a dog, until you weigh two of them. The breed catalogue holds a roughly hundredfold spread from its lightest to its heaviest, and both ends are measured rather than rounded up for effect.
At the bottom sits the Chihuahua, whose adults start at about 1 kg. At the top, the Spanish Mastiff reaches about 120 kg — the heaviest measured breed here, and over thirty times the weight of the lightest for an animal that is still the same species.
Tall is a different record from heavy
Weight and height do not crown the same breed. For height, the Great Dane tops out around 90 cm at the withers — among the tallest measured here, leggier than the Spanish Mastiff but lighter, because height and mass are measured separately and a breed can lead one without the other.
The giant end is not a handful
Around thirty breeds classify as giant — the top size band, derived from measured weight rather than reputation. Every one is on the breeds page with its own numbers, so the size chart is checkable rather than asserted.
Every figure here is measured from public sources and shown on each breed's page with the source it came from. Where a breed's weight was never recorded, the page leaves it blank rather than guessing.
What is the heaviest dog breed?
In this catalogue, the Spanish Mastiff, whose adults reach about 120 kg — the highest measured weight of any breed here.
What is the lightest dog breed?
The Chihuahua, from about 1 kg, which makes the heaviest breed over thirty times its weight.
Which breeds are tallest?
The Great Dane reaches about 90 cm at the withers, among the tallest measured here. Height and weight are measured separately, so the tallest breed is not the heaviest.