Cat years to human years – 4 ways to work it out accurately

Here are 4 ways to work out cat years to human years and vice versa. The calculator at the end of the article is a useful third-party gizmo. It will do the math for you. The spreadsheet data below contains two sources for accuracy. In the middle are Dr Bruce Fogle’s calculator and Ruth’s chart.

Cat life stages
Cat life stages chart
Two useful tags. Click either to see the articles:- Toxic to cats | Dangers to cats

A notable feature of comparing cat age to human age is that you cannot simply multiply a cat’s age by a certain figure to come to a figure for human age as a cat ages faster during the first two years of its life compared to humans. This prevents us using a simple calculation. I have included a multiplier on the RHS of the spreadsheet and, as can be seen, the factor varies throughout. Also, the chart shows estimates. This is because individual cats age at different rates.

It is said that the ‘average’ house cat lives to 15 years of age1, with many cats living well into their 20s. A cat’s lifespan depends on:

  • Inherited genetics
  • Nutrition
  • Environmental issues such as stress levels
  • Whether the cat is purebred or random bred

In the wild the situation is different. I have read that feral cats live to three years but 6 years is also quoted. The well-known charity Alley cat Allies correctly states that if feral cats are part of a colony cared for by TNR volunteers their lives can be quite good to very good. They can live to an age which is comparable to that of a domestic cat. We should not make the assumption that all feral cats live short, miserable lives as stated by PETA. I’m afraid that this is incorrect even though I support PETA.


The differences between the domestic and feral cat in terms of factors that affect age can be summarised as follows:

FactorDomestic CatFeral Cat
Exposure to accidentsLimitedHigh
Exposure to diseaseLimitedHigh
Elderly Lady with Loyal Cat
Elderly Lady with Loyal Cat. They have grown older together.

Dr. Bruce Fogle’s DVM age calculator from his book Complete Cat Care

I think that it is useful to throw into the ring another person’s method for calculating cat age compared the human age. This is here for the sake of completeness. He states that there is no science but these are his calculations. Dr. Bruce Fogle is a very well-respected veterinarian living in London and a prolific author about cats and dogs and other animals.

On the left is the cat’s age. On the right is the human’s age:

One month = 10 months
Three months = seven years
Six months = nine years
One year = 24 years
Two years = 26 years
Three years = 42 years

From that point on the steps are of three cat years per human year:

Four years = 45 years

And then:

18 years = 87 years
19 years = 90 years
20 years = 93 years

As you can see the comparison is not linear. It is quite lumpy. Which, as explained, prevents a simple multiplication calculation.

Ruth’s chart

This is self-explanatory. Ruth aka Kattaddorra is an experienced cat caregiver living in the north of England.

Age Chart
Age chart – by Ruth AKA Kattaddorra


This is an embedded human-to-cat and cat-to-human years calculator which you might find handy. Please note, however, that this is an embedded tool for this website provided by another website and if that other website deletes the tool and it won’t work here either. You simply enter the years in the first section and the result will immediately show up. You can work out human years from cat years and vice versa. There is a toggle switch to switch over.

Cat years to human years calculators interest people because we want to get a feel how old our cat is in our terms.


1. Cat Owner’s Home Veterinary Handbook by Drs Carlson and Giffin and as stated.

Timelapse from young kitten to full adult – video

Note: This is a video from another website which is embedded here. Sometimes they are deleted at source which stops them working on this site. If that has happened, I apologise but I have no control over it.

1 thought on “Cat years to human years – 4 ways to work it out accurately”

  1. I wonder if it would be possible to select and breed cats, not for appearance or size, as I believe all cats breeds are, but for longevity and resistance to and/or freedom from the common cat ailments, irrespective of appearance, or size? Or would the selective breeding process itself inevitably mitigate against any such goal, because genetic predispositions to ailments would be concentrated, not eliminated? Would this constitute cat eugenics?


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