Relative Size of Solar System, Fractions, Ratios, Percentages, and the Sun

As a child, I would marvel at the pictures of the 9 planets and the sun and dream of becoming an astronaut.dThe astronaut thing didn’t work out but the love of astronomy never went away. When I was in 5th grade, Mr. Cunningham gave me a revelation: all of the pictures of the solar system were completely inaccurate regarding relative size and distance. I couldn’t believe it, so I started researching the diameters of each planet and then converting that to volume ratios. He was right.


So with the help of NASA’s website, here is an activity that you can do with any material that can be cut and formed together such as Play Dough, Model Magic, Dirt, Tofu, Hummus, and one student even used an apple (most creative).


I also gave the children a centimeter ruler on page one:

1 centimeter = 10 millimeters

10 centimeters = 100 millimeters


Take a picture of the solar system in which the 9 planets are labeled on page one of the pdf. This is where you will be placing the Play-doh to make each of the planets in relative size (volume) to each other.


1. Make 10 equal parts. Squash 6 of the tenths (6/10s) together...this will be JUPITER. Place that sphere on the paper labeled JUPITER. Take another 3 tenths and squash them together...this is only part of SATURN (you will add to SATURN two more times before the activity is over). Place the those 3 tenths (3/10s) together on the paper labeled SATURN.


2. Divide the Play-doh that is left into 10 equal parts. Squash 5 of the tenths together and add them to SATURN (if you make that piece the rings, the sphere of Saturn will be about 1/7 less than it should be). Take 2 parts and squash them together...this is NEPTUNE. Place those parts on the paper labeled NEPTUNE. Take another 2 parts and squash them together...this is URANUS (the Latin pronunciation: "yr·ei·nuhs" is not as fun as the common pronunciation: "your anus," which of course makes us all giggle a bit). Place those parts on the paper labeled URANUS.


3. With the Play-doh that is left, make 10 equal parts. Squash 9 of the tenths (9/10s) together...add them to SATURN. SATURN is now complete!


4. Divide the remaining Play-doh into 2 equal parts. 1 part (1/2) is EARTH. Place that part on the paper labeled EARTH.


5. Now is when things get tricky! Divide the remaining Play-doh into 10 equal parts. 9 of the tenths (9/10s) make up VENUS. Place those 9 parts on the paper labeled VENUS.


6. Make 10 equal parts out of the Play-doh that is left. Use 9 of the tenths (9/10s) to  create MARS. Place those 9 parts on the paper labeled MARS.


7. Divide the remaining Play-doh into 10 equal parts. 9 of the tenths (9/10s) make up MERCURY. Place them on the paper labeled MERCURY. And the one tenth (1/10) left is PLUTO! Place that part on the paper labeled PLUTO. 


Why isn't the Sun included in this activity? The Sun is so much larger than all of the planets that whatever amount of Play-doh you used to make the 9 planets, it would take 650 times that amount to make the Sun!



A) Create your own solar system using Play-doh, Clay, Model Magic, Mashed Potatoes, Hummus, Tofu, etc.

B) Label each planet.

C) 2ND GRADE AND UP: Split up the grid of one millimeter squares to show the proportional volume of the planets on page 4.

D) 4TH GRADE AND UP: Identify the ratios between the sizes of each pair of planets on pages 6 and 7.

E)  4TH GRADE AND UP: identify the simplified fraction and percent(%) of each planet of the mass of the whole solar system (for example, Jupiter is 3/5 = 60% of the whole planet mass) on page 3.



THE COLUMN UNDER THE HEADING "PLUTO IS 1" ARE THE RATIOS OF THE PLANETS' SIZES (for example, Earth to Pluto is a 1000 to 1 ratio; we write 1,000:1 or 1,000/1)


THE COLUMN UNDER THE HEADING "EARTH IS 1" ARE THE RATIOS OF THE PLANETS' SIZES (for example, Jupiter to Earth is a 1,200 to 1 ratio; we write 1,200:1 or 1,200/1)


for example, since Mercury is a 9 to Pluto at 1 we say that:

  • the ratio of the sizes of Mercury to Pluto is 9 to 1 or 9:1 or 9/1
  • Mercury is nine times the size of Pluto (Mercury is 900% of Pluto)
  • Pluto is one ninth (1/9) the size of Mercury (Pluto is 11.1% of Mercury)


PLANET RELATIVE SIZE (by volume or mass)





Jupiter 1,200,000 1,200 88,730 _____________

Saturn 718,000   718 74,940 _____________


Neptune          40,000 40 30,775 _____________


Uranus 40,000 40 31,763 _____________


Earth               1,000       1 7,926 _____________


Venus                  900 0.9 7,521  _____________


Mars 90 0.09 4,222 _____________

Mercury           9 0.009          3,031 _____________


Pluto + 1     +    0.001 1,430 _____________

 Total Units 2,000,000  2,000


The Sun    1,300,000,000   1,300,000         865,370


The ratio of Sun to Earth is 1,300,000:1  

The ratio of Sun to Jupiter is 928:1




I also gave the children dozens of Volume Ratio relationships to work on.


Planet Relationship Ratio

Uranus to Neptune 1:1

Mercury to Pluto 9:1

Mars to Pluto 90:1

Venus to Pluto 900:1

Earth to Pluto 1,000:1

Uranus to Pluto 40,000:1

Neptune to Pluto 40,000:1

Saturn to Pluto 718,000:1

Jupiter to Pluto 1,200,000:1

Mars to Mercury 10:1

Venus to Mercury 100:1

Earth to Mercury 1,000:9

Uranus to Mercury 40,000:9

Neptune to Mercury 40,000:9

Saturn to Mercury 718,000:9

Jupiter to Mercury 400,000:3


Venus to Mars 10:1

Earth to Mars 100:9

Uranus to Mars 4,000:9

Neptune to Mars 4,000:9

Saturn to Mars 71,800:9

Jupiter to Mars 40,000:3

Earth to Venus 10:9

Uranus to Venus 400:9

Neptune to Venus 400:9

Saturn to Venus 7,180:9

Jupiter to Venus 4,000:3

Uranus to Earth 40:1

Neptune to Earth 40:1

Saturn to Earth 718:1

Jupiter to Earth 1,200:1

Neptune to Uranus 1:1

Saturn to Uranus 359:20

Jupiter to Uranus 30:1

Saturn to Neptune 359:20

Jupiter to Neptune 30:1

Jupiter to Saturn 600:359




330pm_Relative_Size_of_Planets_Fractions_Ratios.pdf6.73 MB
430pm_Relative_Size_of_Planets_Fractions_Ratios.pdf6.83 MB
530pm_Relative_Size_of_Planets_Fractions_Ratios.pdf6.83 MB