Calculate Percentages In Your Head
Use these tips below to quickly calculate percentages like tip, all without a calculator!
Multiply Whole Numbers
First, always multiply using whole numbers since this is the easiest to do in your head.
Move the decimal over
Percentages represent a number out of 100, so first multiply the whole numbers, then move the decimal point over. Example: 30% (or 30/100) of 90 can be found by multiplying 30 x 90 = 2700. Then, move the decimal place back two places to the left to get the answer 27.
If an exact number isn’t needed, you can always round to the closest multiple for a quick approximation. Example: 40% of 72 can be estimated by multiplying 40x70 = 2800 –> move the decimal over two places –> 28
For harder to multiply percentages (such as 15%, 25%, etc), it is often easier to find another percentage and then manipulate it to get your final number. Here are some common percentages and how to calculate them:
5% = 10% divided by 2
15% = 10% + half of 10%
20% = 10% x 2
25% = 50% divided by 2
60% = 50% + 20%
75% = 50% + 25%
Example: 60% of 200 is equivalent to 100 (50%) + 20 (10%) = 120
Now go on and impress your friends calculating tip the next time your dinner bill arrives!