The Solar System at a glance: eight planets, measured

Eight planets, one spreadsheet. Mean radii, day and year lengths, and moon counts - with live formulas computing how many Earths fit inside each planet.

Values are from NASA's Planetary Fact Sheet (mean radius, orbital periods). Moon counts are the confirmed tallies as of 2024; they keep climbing as surveys find more, so treat that column as a snapshot.

A note on conventions: "day length" here means a solar day - one sunrise to the next. For the gas giants a solar day is effectively their rotation period, but for Mercury and Venus the two differ wildly, which is exactly what makes those rows interesting.

Planets

Planet	Radius (km)	Volume (Earth = 1)	Moons (2024)	Distance from Sun (AU)	Year (Earth days)	Solar day (hours)
Mercury	2440	0.06	0	0.39	88	4222.6
Venus	6052	0.86	0	0.72	224.7	2802
Earth	6371	1	1	1	365.3	24
Mars	3390	0.15	2	1.52	687	24.7
Jupiter	69911	1321.34	95	5.2	4333	9.9
Saturn	58232	763.59	146	9.58	10759	10.7
Uranus	25362	63.09	28	19.2	30687	17.2
Neptune	24622	57.72	16	30.1	60190	16.1

Things worth noticing

• Jupiter's volume works out to about 1,321 Earths. Every other planet combined fits inside it with room to spare.
• Venus spins backwards and so slowly that one full rotation takes 243 Earth days - longer than its 224.7-day year. Yet its solar day, shown in the table, is only about 117 Earth days: the backwards spin makes the Sun cross the sky faster than the planet turns.
• Saturn's moon count overtook Jupiter's in 2023 when 62 new moons were confirmed in one announcement.
• Mercury's solar day is the extreme case: it rotates exactly three times for every two orbits, stretching one sunrise-to-sunrise cycle to 176 Earth days - twice its own year.

Formulas at work

The Volume column is a live formula: =ROUND((B2/$B$4)^3,2) cubes the ratio of each planet's mean radius to Earth's, rounded to two decimals. Change a radius and every volume recalculates. That's the point of a living document - correct the numbers as measurements improve and the comparisons take care of themselves.

Sources: NASA Planetary Fact Sheet (nssdc.gsfc.nasa.gov/planetary/factsheet), IAU moon designations. License: CC-BY-4.0 - reuse freely with credit.