Calculating your dog's age isn't as simple as we previously thought. Dogs age a lot faster at the beginning of their lives, and it's not as easy as 'multiplying by 7.'

You've probably heard someone say their pet is "28 in dog years," and you would do the math and find out the dog is 4-years-old. But, it looks like figuring out a dog's age just got a little harder...

The good people at WebMD, created a handy chart that shows how your dog ages, compared to the previous belief of a cut-and-dry 7 years. According to WebMD, dogs mature a lot faster, earlier in their life. So instead of 1 year being 7 in dog years, it's actually more like 15 years.

According to WebMD's Chart, it also depends on how big of a dog you have. Although for the first few years dogs age at about the same rate, eventually bigger dogs end up aging faster. So let's say you have a big dog, like a Great Dane (or any dog over 50 pounds), according to the Chart, 1 year = 15 years, 2 years = 24 years, and 3 years = 28. According to the old belief, it would be 4 years before your dog aged to 28-years-old. This stays true for all dog sizes up to 4 years. After that, the size of your dog starts playing a factor. For example, at 10 years, if you have a smaller dog (20 pounds or less), your dog will actually be 56. If you have a medium-sized dog (21 pounds to 50 pounds), your dog will actually be 60, and if you have a larger dog (over 50 pounds), your pup will actually be 66-years-old.

As you can tell from those numbers, that's a lot different than the standard 7-years math we've all thought before. And in this case, your dog is actually younger than what was previously thought.

The biggest thing to take away from all this information is that dogs age more drastically in the beginning of their lives than what we previously thought. But on the flip side of that, dogs don't age so fast later in their lives. You can see the chart for yourself and see where your pet falls on the list at: Pets.WebMD.com/Dogs