How to Tell Your Puppy's Age

Co-authored by Deanne Pawlisch, CVT, MA

Last Updated: October 18, 2024 Approved

If you have rescued or found a puppy, you may not know exactly how old they are. Looking at the size of the puppy can give you a rough estimate, but different breeds grow at different rates. The easiest way to determine a puppy’s age is to look at their teeth, assess their behavior, and take them to the vet.

Method 1

Method 1 of 2:

Examining the Teeth

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Puppies who do not have teeth that have grown in yet are newborns. They also probably haven’t opened their eyes and are still spending all their time with their mother. If the puppy has no teeth, they are up to three weeks old.^{[1]
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Canines are the four pointy teeth that dogs have. There are two on the top and two on the bottom. These are the first teeth to come in. They will start to come in between three to four weeks of age.^{[2]
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The incisors are the small teeth in the front of the mouth between the canines. Two sets of incisors will be the next teeth that come in for puppies. They come in around four to five weeks of age.^{[3]
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Premolars are the teeth that are right beside the canines. Between four to six weeks, the first two sets of premolars will grow into the puppy’s mouth.^{[4]
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The last sets of these teeth come a few weeks after the first sets. The last set of incisors will grow in around five to six weeks of age, and the last four premolars will come at six to eight weeks.^{[5]
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By eight weeks, the puppy will have all their baby teeth. They are very sharp. As the puppy grows between eight and sixteen weeks, the head and jaw will grow, which will cause the teeth to have spaces between them. They will also start to look too small for the puppy’s mouth.^{[6]
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Notice the permanent teeth coming in. Between sixteen weeks and eight months, the baby teeth will fall out and be replaced with permanent teeth. They start in the front with the incisors. The teeth will be replaced in order through the mouth. The older your puppy is, the farther back the transitioning between the teeth will be.^{[7]
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- Most baby teeth are all gone by five months, and all adult teeth will be visible between eight to twelve months.

Method 2

Method 2 of 2:

Assessing the Puppy’s Body and Behavior

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Puppies up to two weeks old are tiny in size. They haven’t opened their eyes yet. The puppies do not move around very much and stay close to their mother. They mainly only root, feed from the mother, and sleep.
Puppies open their eyes when they are around two to three weeks old. They start walking and adventuring out of the whelping box during this time. They appear to become more aware of their surroundings and they begin to explore on their own. This is characteristic of puppies up to around five to six weeks old.
Puppies generally get their food from their mother until between five to seven weeks old. Puppies who are transitioning to eating solid foods and who are becoming independent of their mother are probably around six to eight weeks old.
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Watch for increased chewing and playing. As the puppy grows, they start becoming more active. By eight weeks old, the puppy is acting how people typically expect a puppy to act. Because their teeth are coming in, they begin chewing on things. They also begin playing in an energetic manner and exploring everything around them.^{[8]
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- They may also start acting restless or whining due to their teeth.
- They will also spend a lot of time sleeping in between playing and chewing.
Puppies have a growth spurt between eight and sixteen weeks of age, and then they continue visibly growing over the next several months.^{[9]
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As they age, puppies will lose their puppy coats and gain their adult coat. Puppy coats are very soft, while adult coats are denser and thicker.
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Watch for behavioral problems. Puppies who are between six to twelve months old will start testing their boundaries. They get an increase in energy and are distracted easily by everything. They may start chewing more things around the house, and they love to explore and may wander off.^{[10]
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- At this age, the puppy may ignore you and forget behaviors they previously learned.
Most puppies will have reached their full size by the time they are between eight and twelve months old. Larger breeds will continue growing for up to two years. A dog under two years is still considered an adolescent. They have some puppy-like qualities, like chewing and energy, but they may have calmed some.^{[11]
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Unspayed female dogs typically have their first heat at 6-24 months old. You can tell that your dog is in heat if she’s nervous, very alert, and gets distracted easily. You also might notice that her vulva is swollen, or producing blood-tinged or straw-colored vaginal discharge.^{[12]
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A male puppy’s testicles should descend into its scrotum within the first 7 weeks after birth. You’ll be able to tell because the testicles will be much more noticeable.^{[13]
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Take the puppy to the vet. If you are unable to figure out how old the puppy is based on the teeth or developmental stage, you can take them to the vet. The vet will be able to look at the size and breed, along with the teeth, and give you a fairly accurate estimated age.
- Whenever you first get a puppy, you should take them to the vet to get a checkup. The vet can tell you their age during your first visit.