How to tell a dog’s age?

A dog’s age is generally estimated from its teeth. Puppies under 20 days old have no teeth; around 20 days they start teething, and by about 2 months the baby teeth are complete – 28 white teeth. Between 3 and 4 months they begin losing teeth, normally finishing by 7-8 months, after which the dog has 48 teeth.

At 1 year the teeth are bright and white; at 1.5 years the tip of the lower first incisor shows wear, and at 2.5 years the lower second incisor wears. Wear continues at 3.5 (upper first), 4.5 (upper second), 5 (lower third), 6 (canines round), 7 (lower first worn to root), 8 (lower first tilts); after 10 years teeth may start falling out.