How old your dog REALLY is: Why multiplying ‘human years’ by seven is a myth – and the biological calculator that reveals your pup’s ‘true age’

If you want to calculate the age of your dog, multiply the number of years they’ve been alive by seven.

That is the old cliché — but is it true?

Sadly it’s not that simple, experts say, firstly because it differs from breed to breed but also because our canine companions age at a different rate to us.

For example, it takes humans 18 years to reach adulthood. But because dogs often undergo puberty – or their teenage phase – at around six months, they are only puppies until about nine months at the latest.

So how else can we work out a dog’s ‘true age’? MailOnline takes a look — including how a biological calculator is just one of the alternatives to the 7:1 year ratio.

How can we work out a dog’s ‘true age’? MailOnline takes a look — including how a biological calculator is just one of the alternatives to the 7:1 year ratio. A new formula has been created by researchers at the University of California (pictured) and is based on the rate that molecules are added to DNA as we age

Varying: Part of the problem of trying to create a one-size-fits-all approach to a dog’s age is that it often differs depending on the breed, size and gender of the pooch (stock image)

This new formula was created by researchers at the University of California and is based on the rate that molecules are added to DNA as we age.

These molecules are known as methyl groups, which can change functions and are known as ‘epigenetic’ changes.

The scientists looked at these changes in the nucleic acid (called methylomes) of 104 labradors and compared them with those of humans.

They found that although the relationship was not linear, there were similarities in the timing of major milestones between dogs and us.

These were particularly strong when similar age dogs and humans were compared. 

However, as discussed above, the team did find that there were periods in the life of dogs where the clocks didn’t match humans, including during puberty as they mature earlier in their lifecycle than humans. 

Nevertheless, the research allowed them to create a ‘biological calculator’ to establish a dog’s ‘true age’.

To establish this human equivalent, the formula involves taking the log of that age, multiplying it by 16, and then adding 31. 

On this basis, an 18-year-old dog would be 77 and a 2-year-old dog would be 42 in ‘human years’.

Try out our calculator above to see how old your dog is by comparison.

Of course, part of the problem of trying to create a one-size-fits-all approach to a dog’s age is that it often differs depending on the breed, size and gender of the pooch.

For example, female dogs live slightly longer than male dogs, while small canines have lifespans that are quite a bit longer than those that are bigger.

One study estimates that small dogs live on average 16.2 human years, compared to 12 years for large dogs. Mixed-breed dogs also tend to live a bit longer than pedigrees, meanwhile.

However, generally speaking if we’re looking at dogs as a whole the life expectancy is around 12.69 years on average.

That is according to a recent study of almost two million dogs who are clients of more than 1,000 vet clinics in the US.

How different pooches compare: Small canines have lifespans that are quite a bit longer than those that are bigger. Generally speaking, however, a dog’s life expectancy is around 12.69 years on average

This graph shows how a dog’s behaviour changes as it ages. Green shows how the brain develops and then starts declining in senior years; orange shows how some traits, like cognitive decline, increase exponentially in a dog’s geriatric years; red shows the slow decline in a dog’s activity and attentiveness 

Separate research has also revealed how dogs become teenagers at just six months old, fully-fledged adults by two and ‘seniors’ at around seven.

‘Dogs mature more quickly than we do,’ said lead study author Dr Naomi Harvey, a research manager at Dogs Trust and an academic at the University of Nottingham.

Disputing the 7:1 year cliché, she added: ‘Many one-year-old dogs have reached their full height and most will have gone through puberty or be approaching the end of it, so they’re definitely not the equivalent of a seven-year-old child!’

Her findings show that a one-year-old dog is a juvenile just finishing puberty, and is akin to a 15-year-old human.

But just 12 months later, at two years old, dogs have reached full maturity in the same way as a 25-year-old person.

Dr Harvey found dogs can be considered to be entering their senior years at age seven and are deemed geriatric at age 12 and over.

The former is defined as being when the animal is older, but healthy, and the latter is when poor health and death become likely.

A dog’s life: University of California researchers have claimed that dogs are middle aged by the time they are two (stock image)

The research shows that aging is defined by various behavioural and cognitive traits and trends.

For example, a dog’s brain is still developing until it is around seven, after which its attentiveness declines, indicting it is now a senior pooch.

Geriatric dogs aged 12 may show signs of being in a bit more pain and also may suffer memory issues, akin to people with dementia.

So just how can you help your dog live longer? Well, keep an eye on its weight for a start.

One study found that a normal-weight Labrador lives 13.6 years if female and 13.3 if male, but if overweight that drops to 13.0 and 12.7 respectively. 

Meanwhile, a normal weight Yorkshire Terrier lives 15.5 years (female) or 16.2 (male), but that drops to 13.5 or 13.7, respectively, if overweight.

Research has also suggested that better dental care may help, too.

But if one thing’s for certain, trying to estimate your dog’s true age on the 7:1 year ratio is perhaps not the most accurate way of doing so.