Planetary age: your age in other planets’ years
Every other system on this site is a calendar — something people built, argued about and use to decide when a festival falls. This one is not. It is one division: the time since you were born, divided by how long a planet takes to go round the Sun. That is worth knowing before reading any number on this page.
What is actually being measured
A year, in this sense, is one orbit. The figure used here is the sidereal orbital period — the time a planet takes to return to the same position against the background stars — which is the number the fact sheets publish and the closest thing to an unambiguous definition of a planet’s year.
Nothing else about a calendar carries over. Mars has no months, no weeks and no dates; there is no Martian new year, because nobody has ever needed one. So “your age on Mars” is a ratio dressed up in the language of birthdays, and the interesting part is the ratio: Mars takes almost twice as long to go round, so the number is a bit over half the Earth figure.
| Body | Symbol | Orbital period (Earth days) | Orbital period (Earth years) |
|---|---|---|---|
| Mercury | ☿ | 87.969 days | 0.2408 Earth years |
| Venus | ♀ | 224.701 days | 0.6152 Earth years |
| Earth | ♁ | 365.256 days | 1.0000 Earth years |
| Mars | ♂ | 686.980 days | 1.8808 Earth years |
| Jupiter | ♃ | 4,332.589 days | 11.8618 Earth years |
| Saturn | ♄ | 10,759.220 days | 29.4567 Earth years |
| Uranus | ♅ | 30,685.400 days | 84.0107 Earth years |
| Neptune | ♆ | 60,189.000 days | 164.7858 Earth years |
| Pluto (dwarf planet) | ♇ | 90,560.000 days | 247.9357 Earth years |
Pluto is on the list because it is interesting and because people look for it, not as a claim about its status: the International Astronomical Union reclassified it as a dwarf planet in 2006, and the table says so.
A worked example
Someone born on 15 May 1990, as of 20 August 2026. Every figure is computed when this page is built, by the same module the calculator uses.
| Body | Age in its years | Complete orbits | Current orbit completes in |
|---|---|---|---|
| Mercury | 150.579 Mercury years | 150 | 38 Earth days |
| Venus | 58.951 Venus years | 58 | 12 Earth days |
| Earth | 36.266 Earth years | 36 | 269 Earth days |
| Mars | 19.282 Mars years | 19 | 494 Earth days |
| Jupiter | 3.057 Jupiter years | 3 | 4,085 Earth days |
| Saturn | 1.231 Saturn years | 1 | 8,273 Earth days |
| Uranus | 0.432 Uranus years | 0 | 17,440 Earth days |
| Neptune | 0.220 Neptune years | 0 | 46,943 Earth days |
| Pluto | 0.146 Pluto years | 0 | 77,314 Earth days |
Neptune’s year is 164.79 Earth years and Pluto’s is 247.94, both longer than any verified human lifespan, so those two rows will read zero for everyone. Uranus, at 84.01, is the outermost one anybody reaches.
Where these numbers come from
Sidereal orbital period — one full revolution around the Sun, measured against the fixed stars — taken from the NASA planetary fact sheets. An age is elapsed time since birth divided by that period. Source: NASA Goddard Space Flight Center, planetary fact sheets.
These are averages of orbits that are ellipses, not circles, and that perturb each other slightly; the periods are quoted to the precision the fact sheets give and no further. Nothing here is a calendar: no planet but Earth has months, a new year, or a date. A birthday on Mars is a figure of speech for a point in an orbit.
One consequence worth stating plainly, because it makes the Earth row disagree with the Gregorian age on every other page of this site. The sidereal year is 365.256 days; the Gregorian calendar’s average year is 365.2425 days, because it tracks the seasons rather than the stars. The two differ by about twenty minutes a year. For the example above that is the difference between 36.266 sidereal years and 36 years 3 months 5 days on the calendar — the same instant, measured against two different definitions of a year.
Prose last reviewed 2026-08-20.
What this page is not
There is no astrology here. Orbital periods turn up in astrological writing — the roughly 29.5-year Saturn orbit is the basis of the “Saturn return” — and this site takes no position on any of that beyond noting that the orbital period is a measured quantity and the interpretation is not. The number in the table is the measurement.
Nor is it a countdown. The figures above say how much of an orbit has gone by, and that is all they say.