Tip calculator
American practice is to tip on the pre-tax subtotal, though tipping on the total is common and nobody objects. On a $84.50 bill the difference at 18% is roughly a dollar. If the bill already carries a service charge, that is the tip.
Multiply the bill by the tip percentage and divide by a hundred to get the tip, then add it to the bill for the total. Fifteen to twenty per cent is the usual range for table service in the United States; much of Europe rounds up instead, and in Japan tipping is not expected at all.
How to use it
A quick way to do twenty per cent in your head: move the decimal point one place left to get ten per cent, then double it. Eighty-four fifty gives 8.45, doubled to 16.90. For eighteen per cent, take the twenty per cent figure and subtract a tenth of it.
Questions
Convention says tip on the pre-tax amount, but tipping on the total is normal and the difference is small. This calculator tips on whatever number you type in.
Then that is the tip. A line reading "service charge" or "gratuity" on the bill means the staff have been paid, and adding more is optional.
Work out the total here, then divide by hand, or run the calculator once per person on their own share of the bill.
Practice varies widely. Rounding up is common in much of Europe, ten per cent is typical in the UK if service is not included, and in Japan it can cause offence.