Tip calculation formula
Tip = bill × tip rate ÷ 100
Sales tax is calculated from your pre-tax bill. Tip is based on the pre-tax bill unless you select “Tip after sales tax.” Results are rounded to cents before splitting. If the total cannot be divided evenly, the calculator distributes leftover pennies so everybody’s payments add up exactly.
Example: A $100 bill with 8% tax and 20% pre-tax tip has $8 tax, $20 tip, and a $128 total. Split four ways, each pays $32.
Tip before or after tax?
There is no universal convention. Check your receipt and use the calculation that fits your situation.