Cat Age Calculator
Find your cat's actual age and life stage from the 2021 AAHA/AAFP Feline Life Stage Guidelines. The "human years" number is the common rule-of-thumb chart — an analogy, not veterinary science.
Before you start
Method : actual age and 2021 AAHA/AAFP life stage; plus the common 15 / 24 / +4 human-years rule of thumb, clearly labelled.
Checked : stage boundaries and chart tested at 6, 12, 84, 120 and 121 months; sources checked 5 October 2026.
Review : not reviewed by a veterinarian.
Your entries stay in this browser tab; nothing is sent or stored.
Enter your cat's birth date or age.
How to Use This Calculator
- Enter a birth date or the known/estimated age
- Press Calculate
Methodology & assumptions
Actual age: completed calendar months to your local today, or the age you enter (up to 40 years; the record cat lived 38).
Life stage (2021 AAHA/AAFP): kitten under 12 months; young adult 12–83 months; mature adult 84–120 months (7–10 years); senior over 120 months. The guideline says "over 10 years"; this page starts senior the day after the 10th-year mark.
Human-years (rule of thumb): age × 15 to one year; 15 + (age − 1) × 9 to two years; then 24 + (age − 2) × 4. Not taken from the guidelines and not validated.
Worked examples
6 months: kitten; ~8 human-years.
7 y 0 m: mature adult; 24 + 5 × 4 = 44.
10 y 0 m: still mature adult (boundary); 56. 10 y 1 m: senior; ~56.
Understanding your result
Use the life stage for care conversations (exam frequency, diet). The human-years figure is for fun comparison only; rounding means it can shift by a year around birthdays.
Sources & further reading
- Quimby J et al. 2021 AAHA/AAFP Feline Life Stage Guidelines. J Feline Med Surg 2021;23(3):211–233
- Feline Life Stage Guidelines — AAFP (catvets.com)Free-access page. Checked 5 October 2026.
- O'Neill DG et al. Longevity and mortality of cats attending primary care veterinary practices in England. J Feline Med Surg 2015;17(2):125–133Median longevity 14.0 years (IQR 9.0–17.0).
- Oldest cat ever — Guinness World RecordsCreme Puff, 38 years 3 days; sets the 40-year input limit.
Frequently Asked Questions
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