Quadrillion — Definition, Formula & Examples
A quadrillion is the number name for 1 followed by 15 zeros, written as 1,000,000,000,000,000. It equals one thousand trillion.
In the short scale numbering system used in the United States and most English-speaking countries, a quadrillion denotes the integer , which is multiplied by one trillion (). As a power of ten, it occupies the sixteenth place-value position from the right.
Key Formula
Where:
- = Ten raised to the fifteenth power, meaning 10 multiplied by itself 15 times
How It Works
Each named number in the place-value system is 1,000 times the previous one: a million is 1,000 thousands, a billion is 1,000 millions, a trillion is 1,000 billions, and a quadrillion is 1,000 trillions. To write a quadrillion in standard form, you write a 1 and then 15 zeros. Scientists often use the shorthand instead of writing all those zeros. You will see quadrillions used when describing extremely large quantities, such as the number of ants on Earth or distances measured in meters across the solar system.
Worked Example
Problem: Write 3 quadrillion in standard form and in scientific notation.
Step 1: Recall that 1 quadrillion equals 1 followed by 15 zeros.
Step 2: Multiply by 3 to get 3 quadrillion in standard form.
Step 3: Write it in scientific notation by using the exponent 15.
Answer: 3 quadrillion = 3,000,000,000,000,000 =
Another Example
Problem: Scientists estimate there are about 20 quadrillion ants on Earth. How many zeros does that number have when written out?
Step 1: Write 20 quadrillion using the definition of quadrillion.
Step 2: In standard form, this is a 2 followed by 16 zeros.
Answer: 20 quadrillion has 16 zeros when written in standard form.
Visualization
Why It Matters
Understanding large number names like quadrillion builds place-value skills taught throughout elementary and middle school math. In real life, national debt figures can reach into the quadrillions of cents, and scientists use numbers this large when counting molecules or measuring energy in joules. Knowing how to read and write a quadrillion also prepares you for scientific notation, which you will use heavily in science courses.
Common Mistakes
Mistake: Confusing a quadrillion with a trillion or quintillion by miscounting zeros.
Correction: Remember the pattern: million (6 zeros), billion (9), trillion (12), quadrillion (15), quintillion (18). Each step adds exactly 3 zeros.
Mistake: Mixing up the short scale and long scale: in some European countries, a "quadrillion" means , not .
Correction: In the U.S. and most English-speaking countries, the short scale is used, where a quadrillion is . Be aware of which system is being used in your context.