A tip is a percentage of your bill, typically 15% to 20% for sit-down restaurants. Tip Amount = Bill × Tip Percentage (as a decimal) Total = Bill + Tip
Quick Mental Math Methods
20% Tip (the easiest)
Find 10% (move decimal left), then double it.
Bill: $45.00
10% = $4.50
Double it: $4.50 × 2 = $9.00 tip
15% Tip
Find 10%, then add half of that (which is 5%).
Bill: $60.00
10% = $6.00
5% = $3.00 (half of 10%)
15% = $6.00 + $3.00 = $9.00 tip
18% Tip
Find 20% and subtract a little, or find 10% + 5% + 3%.
Bill: $50.00
20% = $10.00
2% = $1.00 (1/5 of 10%)
18% = $10.00 − $1.00 = $9.00 tip
Tip on the Pre-Tax Amount
Technically, you should tip on the pre-tax bill, not the total after tax. In practice, the difference is small — but if you want to be precise, look for the subtotal line before tax is added.
💡 Rounding trick: Round the bill to the nearest $10 first, then calculate the tip. A $47 bill rounds to $50. 20% of $50 = $10. Close enough and much faster in your head.
🎯 Practice Problems
1. Your bill is $40. What is a 20% tip?
A) $4
B) $6
C) $8
D) $20
2. Your bill is $80. What is a 15% tip?
A) $8
B) $12
C) $15
D) $16
3. Your bill is $55. What is a 20% tip?
A) $5.50
B) $11
C) $55
D) $15
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🎯 Bonus Practice
1. Your bill is $30. You leave a $6 tip. What percent tip is that?
A) 6%
B) 10%
C) 15%
D) 20%
2. Your bill is $72. What is a 15% tip?
A) $7.20
B) $10.80
C) $14.40
D) $15
3. Your bill is $50. What is an 18% tip?
A) $7
B) $9
C) $10
D) $18
4. Your dinner bill is $95. Using the rounding trick, what is a quick 20% tip?
A) $19
B) $20
C) $9.50
D) $15
5. You and a friend split a $60 bill evenly and each leave a 20% tip. How much does each person pay total?