How much should you tip? That depends on quality of service as well as whether you are at a sit-down restaurant or a place of less-than-full service. Here are guidelines for calculating 5%, 10%, 15%, and 20%.

• To calculate any percentage of your check, round off the amount to the nearest dollar: Round up if the cents are more than 50; round down if less. If the cents are less than 50 and you feel guilty about not tipping on the cents, then round up just so you feel better.
• If your check is over \$100, you may want to round off to the nearest \$10, to make your calculation easier. If you’re OK with even more approximating, you may want to round off even a number less than \$100 to the nearest \$10. For example, for \$37.23, you might use \$40 for your calculation.

To calculate 10%:

10% is 0.1. To multiply by 0.1, slip the decimal point one place to the left: 10% of \$37.00 = \$3.70. So a tip of 10% on a \$37.23 check is about \$3.70.

To calculate 5%:

Find 10%. See 10% calculation above. That’s \$3.70.

Divide that in half. 5% of \$3.70 = \$3.70/2 = \$1.85. So a 5% tip on a \$37.23 check is about \$1.85.

To calculate 20%:

Find 10%. See 10% calculation above.

20% is twice 10%, so double the 10% amount: 2*\$3.70 = \$7.40. So a 20% tip on a \$37.23 check is about \$7.40.

To calculate 15%. This is probably the hardest one to do in your head. If you’re at a place with paper napkins, one may be convenient just now.

Calculate 10%. (See above.) That’s \$3.70.

Calculate 5%. That’s half of 10%, so divide your 10% result in half. \$3.70/2=\$1.85.

At this point, if you feel you have too many digits. You may want to round off. Round \$1.85 to \$1.90.

10% + 5% = 15%, so combine your 10% and 5% results: \$3.70 + \$1.90 = \$5.60. So a 15% tip on \$37 is \$5.60.

Alternative way to add \$1.90 + \$3.70: Notice that \$1.90 is 10 cents less than \$2.00. Instead of adding \$1.90, try adding \$2 and subtracting \$0.10: \$3.70 + \$2 = \$5.70. \$5.70 – \$0.10 = \$5.60.

This method entails more steps than does just adding \$3.70 and \$1.90, but the steps are easier, especially once you get used to doing it that way.