To find your age on another planet, divide the number of days you have lived by the length of that planet's year in Earth days. A year on Mars is 687 Earth days, so a 36-year-old is about 19 in Mars years; on Mercury, whose year is 88 days, they would be about 151.
The calculator counts your days exactly and uses NASA's orbital periods for all eight planets and Pluto. It also tells you when your next birthday falls on each one — on Mercury, that is never more than 88 days away.
Worked example
Date of birth: June 15, 1990Age on: October 30, 2026
Your age on Mars: 19.34 Mars years
Born June 15, 1990, on October 30, 2026 you have lived 13,286 days. A year on Mars is 686.98 days, so 13,286 ÷ 686.98 = 19.34 Mars years — and on Mercury, whose year is 88 days, that is 151 birthdays.
Open this example in the calculator →How to use the Planet Age Calculator
- Enter your date of birth.
- Leave "Age on" as today, or choose another date.
- Read your age on Mars and every other planet.
- See the date of your next birthday on each planet — and share the card.
How long is a year on each planet?
| Planet | One orbit of the Sun | A 30-year-old is |
|---|---|---|
| Mercury | 88.0 Earth days | 124.6 |
| Venus | 224.7 Earth days | 48.8 |
| Earth | 365.25 days | 30 |
| Mars | 687.0 Earth days (1.88 years) | 15.9 |
| Jupiter | 11.86 Earth years | 2.53 |
| Saturn | 29.46 Earth years | 1.02 |
| Uranus | 84.0 Earth years | 0.36 |
| Neptune | 164.8 Earth years | 0.18 |
| Pluto (dwarf planet) | 248 Earth years | 0.12 |
The farther a planet is from the Sun, the longer its orbit and the slower its years go by — Kepler's third law. Saturn takes almost 29½ years, so your first Saturn birthday — the "Saturn return" of astrology — comes at about 29. Neptune was discovered in 1846 and completed its first orbit since then only in 2011.
Years and days are different things
A planet's year is one trip around the Sun; its day is one turn on its axis. They can be very different: a day on Venus (243 Earth days to turn once) is longer than its year, while Jupiter turns in under 10 hours. The calculator counts years. For Mars it also counts sols — the Martian solar day of 24 hours 39 minutes that rover teams work to.
How the calculation works
- Count the days from your date of birth to today.
- Divide by the planet's sidereal orbital period in Earth days — Mars: 686.98.
- The whole number is how many birthdays you have had there; the next one falls on the day the next whole orbit completes.
Frequently asked questions
How old am I on Mars?
Divide your age in days by 686.98, the length of a Mars year in Earth days. A 30-year-old is about 15.9 in Mars years; a 36-year-old about 19.
Which planet would make me the oldest?
Mercury. Its year is only 88 Earth days, so you have about 4.15 Mercury birthdays for every Earth birthday.
How long is a year on Jupiter?
About 11.86 Earth years (4,332.6 days). Most people have only a few Jupiter birthdays in a lifetime.
Will anyone have a birthday on Neptune?
Only someone who lives to about 164 years and 9 months, the length of Neptune's orbit. On Pluto it would take 248 years.
Why is Pluto included?
Pluto has been classed as a dwarf planet since 2006, but people still like to know their Pluto age, so it is shown at the end of the list.