Tipping
Tip from the bill
One multiplication. The rate is the percentage written as a decimal, so eighteen per cent is 0.18.
The Formula
tip = bill x rate
One multiplication. The rate is the percentage written as a decimal, so eighteen per cent is 0.18.
| Symbol | Meaning | Unit | Notes |
|---|---|---|---|
| bill | Amount the tip is calculated on | currency | Decide once whether this is the pre-tax subtotal or the tax-inclusive total. |
| rate | Tip percentage as a decimal | dimensionless | 18 per cent is 0.18, 20 per cent is 0.20, 15 per cent is 0.15. |
| tip | The gratuity itself | currency | For 85.50 at 0.18 this comes to 15.39. |
What Each Symbol Means
billcurrency
Amount the tip is calculated on
Decide once whether this is the pre-tax subtotal or the tax-inclusive total.
ratedimensionless
Tip percentage as a decimal
18 per cent is 0.18, 20 per cent is 0.20, 15 per cent is 0.15.
tipcurrency
The gratuity itself
For 85.50 at 0.18 this comes to 15.39.
See It Worked With Real Numbers
A formula on its own does not tell you which number goes where. The how to calculate a tip page applies this equation to a concrete case, shows every intermediate step, and names the mistakes that produce a wrong answer even when the algebra is right.
Where This Formula Appears
This equation is the working core of How To Calculate A Tip, filed under Everyday Life. Every number the guide produces comes from substituting into this one line.