Calculating tip in your head is very simple. If you live in an area where the sales tax is between 7% and 8.5% it’s extremely easy to calculate in your head. You simply double whatever the sales tax is and you get around 15% of the total bill. If you don’t want to use that method however, there is another simple way to calculate the tip in your head:
1) Suppose your bill is $18.77 and you want to leave a 15% tip. The first thing you want to do is round up or down to the nearest dollar. In this case you round up to $19.00.
2) Next, you move the decimal to the left one space to get $1.90. (This is 10% of the total bill.)
3) Now round $1.90 to the nearest dollar which is $2.00 (Still pretty close to 10%).
4) Divide by 2 to get $1.00. (This is 5% of the total bill. 10% + 5% =15%)
5) Now add $1.00 to $2.00 and you get $3.00 which is approximately 15% of the total bill.
If you used a calculator you would see that $2.82 is exactly 15% so your estimate was only 18 cents off. If you round down on step 3 you might want to add 50-75 cents to your calculation just to make sure you don’t shortchange your server. If you feel ok leaving a little extra always round UP.
NOW, suppose you want to calculate a tip of 20% in your head. That’s even easier!
1) Suppose your bill is $156.22. Again, the first thing you want to do is round to the nearest dollar which gives you $156.00.
2) Again move the decimal place 1 place to the left to get $15.60, 10% of the bill.
3) If you feel comfortable with doubling $15.60 in your head go ahead and double it to get $31.20, 20% of the bill. If not round $15.60 to the nearest dollar which is $16.00.
4) Double $16.00 to get $32.00. This is approximately 20% of the total bill.
If you use a calculator to determine the tip on $156.22 you would get $31.24. Pretty close! If you want to master this technique play with a couple of hypothetical amounts using the guidelines outlined above (don’t forget to pad the total if you round down on step 3) until you get the hang of it.