SpaceFor a ten-year-old
| World | Its year, in Earth days | Age of someone who is 10 on Earth |
|---|---|---|
| Mercury | 88 | 41.5 |
| Venus | 224.7 | 16.25 |
| Earth | 365.2 | 10 |
| Mars | 687 | 5.32 |
| Jupiter | 4,331 | 0.84 |
| Saturn | 10,747 | 0.34 |
| Uranus | 30,589 | 0.12 |
| Neptune | 59,800 | 0.06 |
| Pluto | 90,560 | 0.04 |
Figures: NASA NSSDCA Planetary Fact Sheet, last updated by NASA on 18 March 2025, read on 12 November 2026.
How it is worked out
Your age in Earth years is multiplied by the length of Earth's year, 365.2 days, to get the days you have lived. That is divided by the length of the other planet's year. You have lived the same length of time whichever planet you count on. Only the size of the unit changes.
Things to notice
- Mercury's year is only 88 Earth days, so you would have about four birthdays there for every one on Earth.
- On Mars your age would be a little over half your Earth age.
- Jupiter takes almost twelve Earth years to go round once, so a twelve-year-old would be just about one Jupiter year old.
- Nobody lives to their first birthday on Uranus (84 Earth years), Neptune (164) or Pluto (248).
Birthdays and days
A year and a day are different things. A planet's year is set by its trip round the Sun, and its day by its own spin. On Mercury a single day, from noon to noon, lasts about two of its years. More on the page about days and years.
An idea for a class
Ask each child to work out their age on Mars by hand first: multiply the age by 365.2 and divide by 687. Then check with the calculator. It is a division sum with a reason behind it, and the answers start a good argument about what a birthday really is.
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