Tip Calculator & Bill Splitter

Quick tip reference

Two ways to tip in your head

The 10% anchor. Move the decimal point one place left to get 10%. Half of that is 5%. So 20% is the 10% figure doubled, 15% is 10% plus half again, and 25% is 10% doubled plus 5%. On an $86 bill: 10% is $8.60, so 20% is $17.20 and 15% is $12.90.

The tax shortcut (US). In places with sales tax around 8–9%, doubling the tax line on the receipt lands close to a 16–18% tip. It is rough, but it is fast and it uses a number already printed in front of you.

Tip before tax, or after?

Convention in the US is to tip on the pre-tax subtotal, though plenty of people tip on the total for simplicity — on a $100 bill with 8% tax, the difference is about $1.60 at 20%. Neither is wrong. What matters more is checking whether a service charge is already on the bill, which is common for larger groups and means the tip line has often been covered already.

Splitting a bill that isn't even

Even splits are easy. The awkward case is when three people shared appetisers and one person only had a salad. The usual approach — work out each person's items, then add their share of tip and tax proportionally — means holding several running totals at once, which is exactly what a single calculator cannot do.

This is the everyday version of the problem CalcBoard was built for: one panel per person, all visible at the same time, with a shared tray for passing the subtotal around. Two panels are free.

Frequently Asked Questions