The physical density of any object is simply its mass divided by its volume; density is measured in units such as pounds per cubic foot, grams per cubic centimeter or kilograms per cubic meter. When calculating the density of a planet, look up its mass and radius, the latter of which is the distance from the surface to the center. Because planets are roughly spherical, calculate the volume of a sphere using the radius. Then divide the mass by the volume of the sphere to get the density.
Things You'll Need
- Scientific Calculator
Find the planet’s mass and diameter. For example, Earth’s mass is about 6,000,000,000,000,000,000,000,000 kg and its radius measures 6,300 km.
Enter the radius in the calculator. Multiply by 1,000 to convert kilometers to meters. Cube this number by pressing the "x^3" key; alternatively, you can press the "x^y" key, enter the number three and then press "equals." Multiply by the number pi -- or 3.1416 -- multiply by four and then divide by three. Store the result by pressing the "M+" or other memory key. The figure you see is the planet’s volume in cubic meters. To continue the example, 6,300 km times 1,000 meters/km = 6,300,000 meters. Cubing it gives 250,000,000,000,000,000,000. Multiplying by pi times 4/3 yields 1,047,400,000,000,000,000,000 cubic meters.
Key the planet’s mass into the calculator. Press the divide key, then recall the volume figure stored in the calculator’s memory. Press the equals key. This result is the planet’s density in units of kilograms per cubic meter. In our example, dividing 6,000,000,000,000,000,000,000,000 kg by 1,047,400,000,000,000,000,000 cubic meters results in a density of about 5,730 kg per cubic meter.
Tips & Warnings
- If you have the planet’s diameter instead of its radius, divide it by two to get the radius.
- Photo Credit forplayday/iStock/Getty Images
How to Calculate Density
Those who have ever read a chemistry or physical science book have probably come across the term density at some point. Density...
How to Calculate Plant Density
Plant density -- the number of plants of a certain species in a particular area -- is determined by counting the number...
How to Calculate Density, Volume, and Mass
Mass, density and volume are mathematically related. If you have two of the terms, you can use them to calculate the third....
How to Calculate Average Mass
Suppose you had a jar of marbles, and you wanted to know the average mass of just one of the marbles. You...
How to Determine the Average Density of a Planet
To find the average density of a planet, you can either derive your own values for mass and volume by combining equations...
How to Calculate the Mass of the Earth's Atmosphere
We live at the bottom of an ocean of air, even if we're not always aware of this. Earth's atmosphere, like all...
The Characteristics of the Eight Planets
Our solar system has eight recognized planets, each with its unique characteristics. There are two main types of planets in the solar...
10 Interesting Facts About Saturn
It's easy to enumerate more than 10 interesting facts about Saturn, the sixth planet in the solar system. The outermost planet visible...