Gratuity of 15 Percent

• 1). Look at the total amount of the bill before taxes.
  
  
• 2). Figure 10 percent of the bill. For examples, if the bill totals $55.15, move the decimal point one space to the left. This amount, $5.515, equals 10 percent of the bill.
  
  
• 3). Drop off the last digit of the number.
  
  
• 4). Divide the resulting number, $5.51, by 2. This answer is 5 percent of the tip. In this case, the answer is $2.755. Again, drop the last digit.
  
  
• 5). Add the two answers together. The amount of 10 percent is $5.51 and the amount of 5 percent is $2.75. The total equals 15 percent — in this case, $8.26.
  
  

Gratuity of 20 Percent

• 1). Look at the total bill before taxes.
  
  
• 2). Figure out what 10 percent of the bill is. For example, if the bill equals $32.69, move the decimal over one place to the left to determine 10 percent of the bill, in this case $3.269. Write this amount down.
  
  
• 3). Drop off the last number, in this case, the "9." That leaves you with $3.26.
  
  
• 4). Double this number to arrive at 20 percent. Add the two numbers together or multiply, using the paper and pencil to figure out your answer if needed. In this case, $3.26 plus $3.26 equals $6.52.