Tipping math trips people up only because they try to do it the hard way. With one simple anchor — 10% — you can hit every common tip percentage in seconds without a calculator.
Start with 10%
Ten percent is just the bill with the decimal moved one place left. A $46.80 bill has a 10% tip of $4.68. That single move is the foundation for everything else.
Build the rest from there
For 20%, double the 10% figure: $4.68 becomes about $9.35. For 15%, take the 10% amount plus half of it: $4.68 + $2.34 = about $7. For 18%, land between 15% and 20%, closer to 20% — roughly $8.40 here. Rounding to a clean dollar is completely fine.
The tax shortcut
In many places sales tax is close to 8–9%, so doubling the tax line on your receipt lands near an 18% tip with zero calculation. Handy when the bill already prints the tax.
Frequently asked questions
Do I tip on the pre-tax or post-tax total?
Etiquette says pre-tax, but the difference is small and many people just use the total for simplicity.
How do I split a tip among friends?
Calculate the total with tip first, then divide by the number of people — dividing then tipping gives the same result.
Try it yourself
Skip the manual math — use a free tool and get the answer instantly:
Results are general information only and not professional financial, medical, or legal advice.