Formula and mental-math guide
How to Calculate a Tip
Learn the standard tip formula, verify each step, and use fast mental shortcuts for the percentages people encounter most often.
Practice the tip formula
The basic tip formula
Convert the percentage to a decimal, multiply by the chosen bill amount, then add the result to the bill when you need the final total.
10%
Move the decimal one place left. Ten percent of $64.50 is $6.45.
15%
Calculate 10%, then add half of that amount. $6.45 + $3.225 ≈ $9.68.
20%
Double the 10% amount. Two times $6.45 is $12.90.
How to estimate 18% quickly
Start with 20%, then subtract 2%. Because 2% is one-fifth of 10%, the arithmetic remains manageable.
| Bill | 20% | 2% | 18% |
|---|---|---|---|
| $40 | $8.00 | $0.80 | $7.20 |
| $60 | $12.00 | $1.20 | $10.80 |
| $100 | $20.00 | $2.00 | $18.00 |
Choose the correct tip base
The formula is simple, but the base may be the pre-tax subtotal, the post-tax amount or the original pre-discount value. Keep the base explicit so your result matches your intention.
Compare tipping before and after tax before relying on a payment terminal’s suggested amount.
Explore the Tip Calculator resource cluster
Use the pillar, calculators and decision guides as one connected system.
Core pillar and calculators4 links
Decision and formula guides3 links
Related calculators and guides
Continue with the most relevant next step.
Frequently asked questions
What is the easiest way to calculate a 20% tip?
Find 10% by moving the decimal one place left, then double it.
How do I calculate a 15% tip mentally?
Find 10%, calculate half of that amount for 5%, then add the two values.
How do I calculate an 18% tip?
Calculate 20% and subtract 2%, or multiply the bill by 0.18.
Do I multiply by 20 or 0.20?
Multiplying by 0.20 gives the tip. Multiplying by 20 would make the result one hundred times too large.
What bill amount should I use?
Use the subtotal or other tip base that matches your chosen rule, and check for tax, discounts and included charges.
Methodology and sources
The interactive example uses standard percentage arithmetic. The mental methods decompose a percentage into easier 10%, 5% and 2% components.