How Old Would You Be on Other Planets? Understanding Planetary Years

Table of Contents — How Old Would You Be on Other Planets? Understanding Planetary Years

What Exactly Is a Year?
Why Every Planet Has a Different Year
Your Age Across the Solar System
The Maths Behind Orbital Periods
Why This Matters Beyond Fun Facts
Converting Your Age Step by Step
Common Questions

What Exactly Is a Year?

When you say "I'm 30 years old," you're really saying "Earth has orbited the Sun 30 times since I was born."

A year isn't some universal measurement. It's just one complete trip around the Sun.

Earth takes about 365 days to complete that trip. But every planet moves at its own pace. Some zip around quickly. Others take decades.

Change the planet, and your age changes too.

On Mars, a 30-year-old Earth person would be about 16. On Jupiter, they'd be just 2.5 years old.

It's the same amount of time lived. Just measured differently.

Why Every Planet Has a Different Year

Two things determine how long a year lasts on any planet:

Distance from the Sun — Farther planets have longer paths to travel
Speed — Farther planets also move slower

These combine to create huge differences in year length.

The Numbers

| Planet | Days to Orbit Sun | Compared to Earth | |--------|-------------------|-------------------| | Mercury | 88 days | 0.24 Earth years | | Venus | 225 days | 0.62 Earth years | | Earth | 365 days | 1.00 Earth year | | Mars | 687 days | 1.88 Earth years | | Jupiter | 4,333 days | 11.86 Earth years | | Saturn | 10,759 days | 29.5 Earth years | | Uranus | 30,687 days | 84 Earth years | | Neptune | 60,190 days | 165 Earth years |

Look at those outer planets. If you were born on Neptune, you wouldn't have your first birthday until you were 165 Earth years old. Nobody would ever reach their second Neptune birthday.

Mercury goes the other way. In one Earth year, Mercury celebrates over 4 birthdays.

Your Age Across the Solar System

Let's take a 30-year-old and see their age on every planet.

Mercury Age: 124 years old

Mercury years are short — only 88 Earth days. You'd have way more birthdays, but they'd come very quickly.

30 ÷ 0.24 = 125 Mercury years

Good news: You're over a century old! Bad news: Each birthday is only 3 months apart.

Venus Age: 48 years old

Venus takes 225 Earth days to orbit, so a Venus year is about 62% of an Earth year.

30 ÷ 0.62 = 48.4 Venus years

You'd be approaching 50. Time to plan a Venus midlife crisis.

Mars Age: 16 years old

Mars takes 687 Earth days — nearly two Earth years — to complete one orbit.

30 ÷ 1.88 = 15.96 Mars years

You'd be a teenager again! Perfect for reliving your youth... or not.

This is actually relevant. Future Mars colonists might use Mars years for some records. A "16-year-old" on Mars could be 30 in Earth terms.

Calculate your exact Mars age with the Age on Mars Calculator.

Jupiter Age: 2.5 years old

Jupiter takes nearly 12 Earth years to orbit the Sun.

30 ÷ 11.86 = 2.53 Jupiter years

On Jupiter, you'd still be a toddler. Your third birthday would be a major milestone — most people never reach it.

Saturn Age: 1 year old

Saturn takes almost 30 Earth years to orbit.

30 ÷ 29.5 = 1.02 Saturn years

You'd have just celebrated your first birthday. Anyone under 30 hasn't had a single Saturn birthday yet.

Uranus Age: 0.36 years old

Uranus takes 84 Earth years to go around the Sun.

30 ÷ 84 = 0.36 Uranus years

You haven't even reached your first birthday. Only people in their mid-80s have celebrated one Uranus birthday.

Neptune Age: 0.18 years old

Neptune's year is the longest — 165 Earth years.

30 ÷ 165 = 0.18 Neptune years

Less than two-tenths of a year old. The planet hasn't even completed one orbit since humans discovered it in 1846.

The Maths Behind Orbital Periods

Why do outer planets take so much longer? There's a elegant rule discovered by Johannes Kepler in the 1600s.

Kepler's Third Law

The relationship between a planet's distance from the Sun and its orbital period follows this pattern:

T² ∝ a³

Where:

T = orbital period (how long a year is)
a = average distance from the Sun

In plain English: If you know how far a planet is from the Sun, you can figure out how long its year is.

Why It Works

Think about it:

Farther planets have longer paths (bigger circles)
But farther planets also move slower (the Sun's gravity is weaker)

Both effects combine. A planet twice as far doesn't just have twice as long a year — it has about 2.8 times as long.

Mars Example

Mars is about 1.52 times farther from the Sun than Earth.

Using Kepler's law:

Distance factor: 1.52
Cubed: 1.52³ = 3.51
Square root: √3.51 = 1.87

Predicted Mars year: 1.87 Earth years Actual Mars year: 1.88 Earth years

The maths works beautifully.

Use the Scientific Calculator to try these calculations yourself.

Why This Matters Beyond Fun Facts

Planetary years aren't just trivia. They affect real things.

Space Mission Planning

Getting to Mars requires precise timing. The planets need to be in the right positions relative to each other.

The best times to launch from Earth to Mars come roughly every 26 months. That's when the orbits align for efficient travel. Miss the window and wait over two years.

This "launch window" is directly calculated from both planets' orbital periods.

Communication Timing

When Mars is on the opposite side of the Sun from Earth, communication is difficult or impossible. Mission planners need to know orbital positions months in advance.

Energy and Power

Mars rovers run on solar power. Mars's elliptical orbit means it's closer to the Sun sometimes and farther at other times. This affects how much energy solar panels generate throughout the Martian year.

Future Calendars

If humans colonise Mars, they'll need a calendar. Will they use Earth years, Mars years, or both?

A "24-month" Mars calendar with months of about 28 sols (Martian days) has been proposed. But nothing is official yet.

People might list ages both ways: "I'm 35 Earth years, or 18 Mars years."

Scientific Records

Researchers studying other planets track events by local years. Martian seasons, atmospheric changes, and surface features are often discussed in Mars years.

Converting Your Age Step by Step

Here's how to convert your age to any planet.

The Formula

Age on Planet = Earth Age ÷ Planet's Year Length (in Earth years)

Example: You're 42 Earth Years Old

Mercury: 42 ÷ 0.24 = 175 Mercury years

Venus: 42 ÷ 0.62 = 67.7 Venus years

Mars: 42 ÷ 1.88 = 22.3 Mars years

Jupiter: 42 ÷ 11.86 = 3.54 Jupiter years

Saturn: 42 ÷ 29.5 = 1.42 Saturn years

Uranus: 42 ÷ 84 = 0.5 Uranus years

Neptune: 42 ÷ 165 = 0.25 Neptune years

Quick Reference Table

Use this table and divide your Earth age by the number:

| Planet | Divide by | |--------|-----------| | Mercury | 0.24 | | Venus | 0.62 | | Mars | 1.88 | | Jupiter | 11.86 | | Saturn | 29.5 | | Uranus | 84 | | Neptune | 165 |

Beyond the Planets

Dwarf Planets

Pluto takes 248 Earth years to orbit the Sun. Even Pluto hasn't completed one orbit since its discovery in 1930.

A 30-year-old would be 0.12 Pluto years old — barely started.

Moons

Moons orbit planets, not the Sun. So they have their own "months" relative to their planet.

For example, Earth's Moon takes 27.3 days to orbit Earth. Titan, Saturn's largest moon, takes about 16 days.

These could matter for future space settlements. A "Titan month" might become a useful time unit.

Exoplanets

Planets around other stars have wildly different years. Some "hot Jupiters" orbit in just a few Earth days. Others take thousands of years.

TRAPPIST-1e, a potentially habitable exoplanet, has a year of just 6.1 Earth days. A 30-year-old would be 1,795 TRAPPIST-1e years old!

Common Questions

Why do some sources give slightly different numbers?

Orbital periods are well-known, but sources round differently. Mars's year is 686.98 Earth days — some round to 687, others to 1.88 years. Small differences, same concept.

Does time actually pass differently on other planets?

Not in terms of physics. Your atoms age at the same rate everywhere. Planetary years are just different counting systems for the same amount of time.

Technically, gravity does affect time (Einstein's relativity), but the difference is tiny for planets. A clock on Jupiter runs very slightly slower than on Earth — but we're talking millionths of a second over years.

If I lived on Mars, would I age slower?

No. Your body ages based on time passing, not planet years. A Mars year is just a longer unit of measurement. You'd still age normally — just count birthdays less often.

How do astronauts track age in space?

They use Earth time. The International Space Station runs on Coordinated Universal Time (UTC). Future Mars missions will likely track both Earth and Mars time.

What about leap years?

Every planet would need leap adjustments. Mars's year is about 668.6 sols (Martian days), so a Mars calendar would need leap days too. The details haven't been standardised yet.

Should I put my Mars age on my CV?

Probably not. But it makes for great conversation.

Try It Yourself

Want to know your exact age on Mars? Use the Age on Mars Calculator.

Curious about how gravity affects your weight across planets? Check the Space Weight Calculator.

For the orbital maths, the Scientific Calculator handles Kepler's equations easily.

The Big Picture

Planetary years remind us that measurements are human inventions.

A "year" isn't some cosmic truth — it's just Earth's trip around the Sun. Other planets, other trips, other year lengths.

But what stays constant is time itself. Whether you measure in Earth years, Mars years, or seconds, you experience the same moments, the same life, the same journey.

You're always exactly as old as you are. The planets just count it differently.

Age on Mars Calculator — Your exact Mars age
Time on Mars Explained — Sols, seasons, and Martian clocks
Weight on Mars — How gravity changes your weight
Space Weight Calculator — Compare weights across planets