How to Calculate a 15% (or 18%) Tip in Your Head

The bill arrives and everyone stares at it. Calculating a tip shouldn't need a spreadsheet. Here's how to work out a 15%, 18% or 20% tip in your head — and split it.

The mental-math trick

10% is easy: move the decimal one place ($46.00 → $4.60). 5% is half of that ($2.30). So 15% = 10% + 5% ($6.90). For 20%, just double the 10% ($9.20). For 18%, take 20% and shave a little off.

Let a calculator handle it

For an exact amount — and to split it between friends — use the tip calculator. Enter the bill, the tip percentage and the number of people, and it shows the tip, the total, and the amount each person owes.

How much should you tip?

Customs vary by country. In the US, 15–20% at restaurants is standard; in much of Europe a small round-up is normal because service is often included; in many Asian countries tipping is minimal. Check the bill for an included service charge before adding more.

Tip on the pre-tax amount

Technically you tip on the food subtotal, not the tax — though many people just use the total for simplicity. On a big bill the difference is small.

Splitting unevenly

If people ordered very differently, split the tip in proportion to what each person's food cost, rather than dividing equally. The calculator's per-person figure assumes an even split.