How old is your Shih Tzu in human years?
Shih Tzus are affectionate seniors — they lean into the slower pace of older life.
Tell us a bit about Your dog
Perfect for a personalized share card.
Don't miss Your dog's next birthday
Free email reminder. We'll send a beautiful note 7 days before, and on the day itself.
Perfect for Instagram, WhatsApp & sharing
On iPhone: long-press the image to save it to Photos.
Based on the UCSD epigenetic aging study (Wang et al., 2020) and breed-specific lifespan data. Estimates only — your vet knows Your dog best.
About Shih Tzu aging
The average Shih Tzu lives between 10 and 16 years, with 13 years being typical. Shih Tzus are affectionate seniors — they lean into the slower pace of older life.
Life stages for Shih Tzus
Based on a typical lifespan of 13 years, here's roughly when your Shih Tzu enters each life stage:
- Puppy: birth to 6 months — rapid physical and mental development.
- Junior: 6 to 12 months — adolescence, social maturation.
- Adult: 1 year to ~7 years — peak health and energy.
- Mature: ~7 to 10 years — early signs of aging may emerge.
- Senior: 10 to 13 years — slower pace, more rest, extra care.
- Golden years: 13+ years — every day is a gift.
How we calculate Shih Tzu age
Our calculator uses the UCSD epigenetic formula published by Wang et al. in 2020, which maps dog age to human age based on DNA methylation patterns. Breed-specific lifespan data comes from the American Kennel Club and peer-reviewed veterinary studies. For a Shih Tzu specifically, this gives you a more personalized result than generic calculators.
Shih Tzu age chart in human years
This table is calculated for the Shih Tzu's own 13-year average lifespan, so the life-stage column differs from a generic dog age chart. Human-year figures use the epigenetic formula; the AAHA column shows the size-adjusted method for comparison.
| Shih Tzu age | Human years (epigenetic) | Human years (AAHA) | Life stage |
|---|---|---|---|
| 1 year | 31 | 15 | Junior |
| 2 years | 42 | 24 | Adult |
| 3 years | 49 | 28 | Adult |
| 4 years | 53 | 32 | Adult |
| 5 years | 57 | 36 | Adult |
| 6 years | 60 | 40 | Adult |
| 7 years | 62 | 44 | Mature |
| 8 years | 64 | 48 | Mature |
| 10 years | 68 | 56 | Senior |
| 12 years | 71 | 64 | Senior |
| 14 years | 73 | 72 | Golden years |
| 16 years | 75 | 80 | Golden years |
Rows stop at 16 years, the upper end of the reported range for this breed. Individual dogs vary — these are population averages, not a prediction for your dog.
How the Shih Tzu compares
At an average of 13 years, the Shih Tzu sits 0.6 years above the 12.4-year average across all 180 breeds we track, and 0.6 years below the 13.6-year average for the 49 small breeds in the dataset. It ranks joint #30 of 49 among small breeds by average lifespan (tied with 14 others), and lives longer than roughly 42% of the breeds we list.
Shih Tzu age: frequently asked questions
How old is a 1-year-old Shih Tzu in human years?
A 1-year-old Shih Tzu is roughly 31 in human years. The UCSD epigenetic formula (16 × ln(age) + 31) puts the first year of a dog's life far ahead of a human's first year, which is why a one-year-old dog is already a young adult rather than a toddler.
How old is a 7-year-old Shih Tzu in human years?
A 7-year-old Shih Tzu is about 62 in human years by the epigenetic method. The older "multiply by seven" rule of thumb would say 49, and the size-adjusted AAHA method gives about 44 for a small dog — the three methods disagree because dogs age fastest early in life, not at a constant rate.
What is the average lifespan of a Shih Tzu?
Shih Tzus live about 13 years on average, with a typical range of 10 to 16 years. Smaller dogs generally have longer average lifespans than larger ones, so the senior threshold arrives comparatively late.
When is a Shih Tzu considered a senior dog?
Using the last quarter of the average lifespan as the senior threshold, a Shih Tzu enters its senior years at roughly 10 years old — about 68 in human terms. Before that, the mature phase runs from around 7 to 10 years.
How much does a Shih Tzu weigh on average?
An adult Shih Tzu averages about 6 kg (13 lb), which places it in the small size class. Size class matters for age conversion because the AAHA size-adjusted method applies a different yearly rate to each class.
At what age does a Shih Tzu reach the human equivalent of 60?
The epigenetic curve crosses human age 60 at about 6.1 dog years — the same for every breed, because the formula is based on DNA methylation rather than breed. What differs per breed is how much of its expected 13-year lifespan remains at that point.
Why do different Shih Tzu age calculators give different results?
Because they use different models. This page reports the UCSD epigenetic clock from Wang et al. (2020), which maps dog age to human age through DNA methylation patterns. The AAHA method instead adjusts by body size, and the "×7" rule is a folk approximation with no research basis. For a Shih Tzu at 10 years the epigenetic method gives about 68 human years.
How old is a 2-year-old Shih Tzu, and a 5-year-old?
A 2-year-old Shih Tzu is roughly 42 in human years and a 5-year-old is about 57. The gap between those two ages is smaller than the gap between birth and age one, because the aging curve is logarithmic — it rises steeply at first and then flattens. Across a full 13-year lifespan a Shih Tzu reaches roughly 72 human years.
Similar breeds
Compare Shih Tzu aging with other breeds
Lifespan is the single biggest factor in how a dog's age maps to human years. These breeds make useful comparisons for a Shih Tzu: