Horses grow up fast in their first four years, then age at about two and a half human years for every horse year.
| Horse age | Human years | Life stage |
|---|---|---|
| 1 year | 6.5 | Youngster |
| 2 years | 13 | Youngster |
| 3 years | 18 | Youngster |
| 4 years | 20.5 | Mature |
| 5 years | 23 | Mature |
| 6 years | 25.5 | Mature |
| 7 years | 28 | Mature |
| 8 years | 30.5 | Prime |
| 9 years | 33 | Prime |
| 10 years | 35.5 | Prime |
| 11 years | 38 | Prime |
| 12 years | 40.5 | Prime |
| 13 years | 43 | Prime |
| 14 years | 45.5 | Middle aged |
| 15 years | 48 | Middle aged |
| 16 years | 50.5 | Middle aged |
| 17 years | 53 | Middle aged |
| 18 years | 55.5 | Middle aged |
| 19 years | 58 | Middle aged |
| 20 years | 60.5 | Senior |
| 21 years | 63 | Senior |
| 22 years | 65.5 | Senior |
| 23 years | 68 | Senior |
| 24 years | 70.5 | Senior |
| 25 years | 73 | Senior |
| 26 years | 75.5 | Senior |
| 27 years | 78 | Senior |
| 28 years | 80.5 | Senior |
| 29 years | 83 | Senior |
| 30 years | 85.5 | Senior |
| 31 years | 88 | Senior |
| 32 years | 90.5 | Senior |
| 33 years | 93 | Senior |
| 34 years | 95.5 | Senior |
| 35 years | 98 | Senior |
A one-year-old horse is like a child of about six or seven. By three they're like an 18-year-old, and by four about 20. After that, each year adds roughly two and a half human years, so a 20-year-old horse is about 60 in human terms.
With good care, many horses and especially ponies live well into their late twenties and thirties, so a "senior" horse may still have years of gentle work and hacking ahead.
About 18. Many horses are started under saddle around this age, though they're still growing.
About 35.5, roughly like someone in their thirties. A horse this age is in the prime stage.
About 48, roughly like someone in their forties. A horse this age is in the middle aged stage.
About 60.5, roughly like someone in their sixties. A horse this age is in the senior stage.
About 73, roughly like someone in their seventies. A horse this age is in the senior stage.
About 85.5, roughly like someone in their eighties. A horse this age is in the senior stage.
Figures follow the commonly published equine age chart and are a rough guide. Horse age charts vary between sources.