30
20% of 150
20%
30 is 20% of 150
+20%
Increase from 150 to 180
How percentage calculations work
A percentage is simply a fraction out of 100. All three calculators above use the same underlying idea, applied differently depending on what you already know and what you're solving for.
Finding a percentage of a number
Multiply the number by the percentage, then divide by 100.
result = (percentage × number) / 100
Finding what percent one number is of another
Divide the part by the whole, then multiply by 100.
percent = (part / whole) × 100
Percentage increase or decrease
Subtract the old value from the new value, divide by the old value, then multiply by 100. A positive result means an increase; a negative result means a decrease.
change % = ((new − old) / old) × 100
Frequently asked questions
How do I calculate a percentage of a number?+
Multiply the number by the percentage and divide by 100. For example, 20% of 150 is (20 × 150) / 100 = 30.
How do I find what percent one number is of another?+
Divide the part by the whole and multiply by 100. For example, 30 out of 150 is (30 / 150) × 100 = 20%.
Can this handle negative numbers?+
Yes, all three calculators accept negative values and will show a negative result where the math produces one, such as a percentage decrease.