Age on other planets
Enter your age, see it in other planets’ years.
How old would I be on Mars?
A year on Mars — one trip around the Sun — takes 686.98 Earth days, about 1.88 Earth years. So a 30-year-old is about 15.95 in Mars years.
How is it calculated?
Your age in Earth days divided by the planet’s orbital period in Earth days. The calculator uses NASA’s sidereal periods, measured against the stars.
Where would I be oldest?
On Mercury, which circles the Sun every 87.97 days — over four Mercury years for every Earth year.
Why are these numbers different from other tables?
NASA’s summary table lists the tropical period (from equinox to equinox); the calculator uses the sidereal periods from NASA’s planet-by-planet fact sheets. The two differ slightly for the outer planets.
Has anyone lived a full year on Neptune?
No — one Neptune year is 60,189 Earth days, about 165 Earth years.
Worked example: a 40-year-old on four planets
Convert the age to days with the Earth’s sidereal year of 365.256 days: 40 × 365.256 = 14,610 days. Divide by each planet’s period. On Mars (686.98 days) that gives 21.27 Mars years, and the next Mars birthday comes in about 503 Earth days. On Jupiter (4,332.589 days) it is 3.37, on Saturn (10,755.699 days) 1.36, and on Neptune (60,189.018 days) only 0.24, since a Neptune year lasts 164.8 Earth years. On Venus (224.701 days) the same person would be 65.0.
What is the difference between a sidereal and a tropical year?
A sidereal period is the time to circle the Sun once relative to the fixed stars. A tropical period is measured from one vernal equinox to the next, so it follows the seasons; NASA’s notes say the tropical period of the Earth is equal to a year on Earth. For Earth the two are 365.256 and 365.242 days, and for Saturn 10,755.699 and 10,746.940 days, a gap of about 0.08%. The planet’s own “birthday” is its return to the same point among the stars, which is the sidereal definition, so the calculator uses the sidereal figure. NASA does not give a reliable tropical period for Pluto and uses the sidereal one, 90,560 days, in its notes.
How long until my first birthday on each planet?
A planet's year in Earth years is its period divided by 365.256 days. The first birthday takes 0.24 Earth years on Mercury (about three months), 0.62 on Venus, 1.88 on Mars, 11.9 on Jupiter, 29.4 on Saturn, 84 on Uranus, 165 on Neptune and 248 on Pluto. A person who lives to 80 Earth years would have had 332 birthdays on Mercury, 130 on Venus, 42 on Mars, 6 on Jupiter and 2 on Saturn, and none yet on Uranus, Neptune or Pluto.
Common mistakes with planet ages
Confusing a planet’s year with its day: the year is one trip around the Sun, while the day is one rotation, and they are unrelated numbers; a Martian solar day, for example, is 24.66 hours. Entering an age in months or in days as if it were years: a 6-month-old is 0.5. Thinking a planetary year must be completed before it counts: 0.24 is a valid Neptune age, meaning about a quarter of the way around. Mixing sources: a table that uses tropical periods gives slightly different ages for the outer planets.
Sources and related calculators
Sources: NASA Goddard Space Flight Center, Planetary Fact Sheets (Earth, Mars, Saturn and Neptune pages for the sidereal and tropical orbit periods) and the fact sheet notes; the other planets’ periods come from the same sheets. Related: weight on other planets calculator, orbital period calculator, age calculator and escape velocity calculator.