How old would you be on Mars?

A year is one trip around the sun. We count the days since you were born and divide by how long each planet takes to go around once: 88 Earth days for Mercury, 687 for Mars, almost 12 Earth years for Jupiter. Pick your birthday above for your exact ages.

Mercury is the closest planet to the sun and races around it in 88 days, so it packs about four of its years into each of ours. The outer planets are the opposite: a Neptune year lasts almost 165 Earth years, so nobody has lived through one.

About half your Earth age, because a Mars year is 687 Earth days. Someone who is 30 on Earth is 15.9 on Mars.

The “times seven” rule is a myth. Vets (the American Veterinary Medical Association) count a medium dog’s first year as about 15 human years, its second as about 9 more, and each year after as about 5. We use that chart in reverse, so a 30-year-old person is about a 3-year-old dog. Small dogs age a little slower and large breeds faster.

Cats follow a similar chart from the American Animal Hospital Association: 15 human years for the first year, 9 for the second, then about 4 a year. A 30-year-old person is about a 3.5-year-old cat.