Percentage Calculator
Calculate percentages, increases, and decreases easily.
Enter Values
A
B
What is A% of B?
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A is what % of B?
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Change from A to B
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The Ultimate Guide to Percentages in Real Life
Percentages are everywhere. From the "30% OFF" sale at the mall to the 20% tip at dinner, understanding how to calculate them quickly is a superpower.UnitMaster makes the complex math simple, but learning the tricks can help you do it in your head.
Mental Math Tricks
Want to impress your friends? Here is how to calculate percentages instantly without a calculator:
- The 10% Rule: To find 10% of any number, just move the decimal point one spot to the left. (10% of $50.00 is $5.00).
- The 20% Tip: Find 10% and verify double it. (Meal is $40 → 10% is $4 → Tip is $8).
- The Swap Trick:
x% of y is exactly the same as y% of x.
Example: You need to find 8% of 25. That sounds hard.
Swap it: Find 25% of 8. That's easy (it's one-quarter). The answer is 2.
Visualizing Percentage Change
One of the most common confusion points is the difference between "Percentage Of" and "Percentage Change".
- Percentage Of tells you a portion. (50 is 50% of 100).
- Percentage Change tells you growth or shrinkage. If a stock goes from $100 to $150, that is a 50% increase. If it drops back to $100, that is a 33.3% decrease. The math is not symmetrical!
The Formula
For those who like algebra, the universal formula for percentage increase/decrease is:
(New Value - Old Value) / Old Value × 100
If the result is positive, it's an increase. If negative, it's a decrease.