The detailed guide below is currently available in English.
The rule behind the conversion
The old "multiply by seven" saying hides how unevenly pets age. Vets commonly use a front-loaded curve: a dog or cat's first year of life builds the equivalent of about 15 human years, the second adds another 9, and every later year adds a steady 4–6 depending on the animal. Size matters for dogs because big breeds age faster and live shorter — a Great Dane is senior years before a Chihuahua — so the yearly increment runs 4 for small dogs, 5 for medium, 6 for large, and 4 for cats of any size.
Life stages, from kitten to geriatric
Pets move through recognizable chapters: the kitten or puppy year of chaotic growth, the junior teenage phase around one to two, a long prime in the middle, then the senior years, and finally geriatric care with twice-yearly vet checks. The labels here follow common veterinary guidance — prime roughly years three to six, senior seven to ten, geriatric from eleven — though large dogs reach each milestone sooner than small ones. Matching food, exercise, and screening to the right stage does more for a pet than any conversion table.
Repères pour la France
Repères locaux pour la France, utiles dans les calculs du quotidien :
- TVA: 20 % en taux normal (5,5 % alimentaire, 10 % restauration) ; les prix sont TTC par loi.
- Monnaie & paiements: Euro (€) ; paiement sans contact et carte bancaire très répandus, virement SEPA instantané en développement.
- Unités & nombres: Système métrique ; virgule décimale et espace pour les milliers : 1 234,56 €.
- Santé: Carte Vitale ; l'Assurance Maladie rembourse en base ≈ 70 % des soins, le reste par mutuelle.
- Pourboire: Service compris : aucun pourboire obligatoire ; arrondir suffit.
Mis à jour : octobre 2026 · valeurs 2025, sources officielles ci-dessus.
Questions fréquentes
Is the "multiply by seven" rule wrong?
Very. A one-year-old cat can reproduce and is finished growing, which no seven-year-old human is. The front-loaded curve — 15 human years in year one, 9 more in year two, then 4–6 per year — tracks development and breed lifespans far better.
Why do large dogs age faster?
Nobody has fully explained it, but across breeds bigger bodies run through their repair budget quicker: Great Danes live around 8–10 years while small breeds often reach 15 or more. The extra human years per birthday reflect that gap.
How accurate is the result for a mixed-breed pet?
Treat it as a fun estimate. Mixed-breed dogs span the size range, and individual health, weight, and genetics shift aging by years in either direction. For medical decisions, your vet reads age alongside bloodwork and body condition, not a formula.