If you are a dog parent, you’ve heard this before – one year for your two-legged family member is equivalent to seven years for your four-legged family member. But how true is this? It turns out the math isn’t that simple.

It is true that dogs age more rapidly than us humans – but several factors come into play on how fast they truly mature.

Dogs age more rapidly early on, so the first year of their life is equal to about 15 human years.

Size and breed matters. Smaller dogs tend to live longer than larger dogs, but they may mature more quickly in the first few years of life. A large-breed canine might age more slowly at first, but be nearing middle age at only five years. Tiny dogs and toy breeds don’t become seniors until around age 10. Medium-sized dogs are somewhere in the middle on both counts.

But don’t worry! No matter how old your dog is, they will always be your puppy.