Age comparison chart
| Pet years | Small · ≤20 lb Human years ≈ | Medium · 21–50 lb Human years ≈ | Large · 51–90 lb Human years ≈ | Giant · >90 lb Human years ≈ |
|---|---|---|---|---|
| 1 | 15 | 15 | 15 | 15 |
| 2 | 24 | 24 | 24 | 24 |
| 3 | 28 | 28 | 30 | 32 |
| 4 | 32 | 33 | 35 | 37 |
| 5 | 36 | 37 | 40 | 42 |
| 6 | 40 | 42 | 45 | 49 |
| 7 | 44 | 47 | 50 | 56 |
| 8 | 48 | 51 | 55 | 64 |
| 9 | 52 | 56 | 61 | 71 |
| 10 | 56 | 60 | 66 | 78 |
| 11 | 60 | 65 | 72 | 86 |
| 12 | 64 | 69 | 77 | 93 |
| 13 | 68 | 74 | 82 | 101 |
| 14 | 72 | 78 | 88 | 108 |
| 15 | 76 | 83 | 93 | 115 |
| 16 | 80 | 87 | 99 | 123 |
| 17 | 84 | 92 | 104 | — |
| 18 | 88 | 96 | 109 | — |
| 19 | 92 | 101 | 115 | — |
| 20 | 96 | 105 | 120 | — |
How to use
Enter your dog’s chronological age in years, then select the group that describes its adult weight. Choose Calculate to see the human-age comparison. For six extra months, add 0.5 to the number of years. This tool compares ages only; you do not need a name, date of birth or account.
The example is ready to calculate. Focusing the age field removes its pale example; leaving it empty restores that example. Editing an input clears the previous result. Calculate again after changing the age or weight group. Copy result copies the estimate with its age, size group and method, so the context travels with the number.
How the comparison works
The numeric reference is the dog table in the AAHA-hosted 2019 physiological-age poster. Each weight group has its own series of values. A whole-year input uses its table entry. Between birthdays, this calculator linearly interpolates between the two surrounding entries; those intermediate values are our arithmetic approximation, not additional observations in the source.
For example, a 5-year-old dog in the 21–50 lb group corresponds to about 37 human years. At 6 years that group corresponds to 42, so 5.5 years gives 39.5. A 10-year-old dog in the 51–90 lb group gives about 66. Multiplying every age by seven would not reproduce these examples.
Choosing the weight group
The original chart uses ≤20, 21–50, 51–90 and >90 lb groups. Use the group based on adult weight rounded to whole pounds, following that chart’s labels. If your scale uses kilograms, 1 lb is exactly 0.45359237 kg. A dog near a boundary should be compared with both adjacent groups, since these categories are coarse guides.
Do not use a growing puppy’s temporary weight to choose its adult group. If adult size is uncertain, compare the plausible groups without presenting one estimate as certain. The calculator does not infer a breed or predict adult size.
Life stages and limits
Puppy, adult and senior describe development and changing care needs; they are not diagnoses. The point at which a dog is considered senior varies with breed and size. A human-age number does not establish a dog’s individual life stage, so this page does not assign a universal senior threshold.
The source starts dogs at 1 year. It ends the largest group at 16 and the other groups at 20. An age outside those limits is rejected instead of extending a table that has no supporting entry. A missing reference is not a statement about whether a dog can reach that age.
Why does another calculator give a different number?
Some use a seven-times shortcut, some use different size charts, and others use research on a particular breed. This page keeps one named reference. Comparing methods can show uncertainty, but averaging unrelated estimates does not turn them into a measured biological age.
Can I use this for a mixed-breed dog?
You can use an adult-weight group for a rough comparison. There is no individual or mixed-breed validation behind the displayed number. Breed, health and an uncertain birthday remain outside this calculation.
Does 66 human years mean my dog will live a certain number of years?
No. The output is an age analogy. It does not estimate lifespan, health status, fitness for exercise or treatment needs. Keep the dog’s actual chronological age when discussing its history.
Can I use months or an estimated birthday?
Use decimal years: 3 months is 0.25 year and 6 months is 0.5 year. Do not enter 5.6 to mean 5 years 6 months. If the birthday is uncertain, compare the youngest and oldest plausible ages; the tool cannot resolve that uncertainty.