BOTTOM LINE: What is the most common element on earth? Oxygen.
On planet earth, oxygen is the most common element, making up about 47% of the earth’s mass. Silicon is second, making up 28%, followed by aluminum (8%), iron (5%), magnesium (2%), calcium (4%), sodium (3%), and potassium (3%).
When combined, all of the remaining elements together make up less than 1% of the earth’s total mass.