How old would I be on Mars?

A Mars year lasts 687 Earth days (about 1.88 Earth years), so your Mars age is your Earth age divided by 1.88. A 30-year-old on Earth is about 16 in Mars years.

Which planet makes you the oldest?

Mercury. Its year is only 88 Earth days, so your Mercury age is about 4.15 times your Earth age — a 20-year-old has lived 83 Mercury years.

Why is a year different on each planet?

A year is one full orbit around the Sun. Planets farther from the Sun have longer orbits, so Neptune's year lasts about 165 Earth years while Mercury's takes just 88 days.

Age on Other Planets Calculator

Why Your Age Changes on Every Planet

Here on Earth, a "year" is one full trip around the Sun — 365.26 days. But every planet takes a different amount of time to complete its own orbit, because planets farther from the Sun have much longer paths to travel and move more slowly. So the same stretch of time equals a different number of birthdays on every world.

Mercury, hugging the Sun, finishes a full orbit in just 88 Earth days. If you are 20 Earth years old, you've already celebrated about 83 Mercury birthdays! At the other extreme, Neptune needs nearly 165 Earth years for one orbit — no human has ever lived to see even a single Neptunian birthday.

Length of a year on each planet

Planet	One year (Earth days)	Compared to Earth
☿ Mercury	88 days	0.24× Earth year
♀ Venus	225 days	0.62×
🌍 Earth	365.26 days	1×
♂ Mars	687 days	1.88×
♃ Jupiter	4,333 days	11.86×
♄ Saturn	10,759 days	29.46×
♅ Uranus	30,689 days	84.01×
♆ Neptune	60,190 days	164.8×

Fun examples

A 10-year-old kid is already 41 in Mercury years — older than their parents in Mercury time!
A 30-year-old adult is only 16 in Mars years and barely 1 in Saturn years.
Anyone over 1 Earth-year old has lived through at least one orbit of Mercury, Venus, Earth and Mars.

Bonus weirdness: on Venus, a single day (243 Earth days) is longer than its entire year (225 Earth days). Sunrise to sunrise takes longer than a birthday cycle!

Curious about your weight in space too? Check the Weight on Other Planets calculator, challenge yourself with our Space Trivia Quiz, or wind down with a round of Astro Dodge.