Tipping 15% used to be the standard advice in US restaurant etiquette guides through the 1990s. By the 2010s, most guides had shifted to 18–20% as the baseline for adequate service, with 20%+ for excellent service. The percentage crept upward gradually, driven by rising menu prices, low base wages for tipped workers in the US, and a general upward drift in service-industry expectations — not by any single rule change.

Why Restaurants Use a Percentage Instead of a Flat Fee

A percentage-based tip scales with the value of the meal, which loosely correlates with the complexity of service — a $200 group dinner with multiple courses generally requires more server effort than a $20 solo lunch. It is an imperfect proxy (a $200 bottle of wine adds cost but not much server effort), which is part of why some upscale restaurants have shifted to a flat service charge instead of an expected tip.

The Mental Math Shortcut

For 20%, the fastest mental calculation is: find 10% (move the decimal point one place left), then double it. A $64.50 bill: 10% is $6.45, doubled is $12.90. For 15%, find 10%, then add half of that 10% figure: $6.45 + $3.23 = $9.68. For 18%, find 10%, double it for 20%, then subtract 2% (one-fifth of the 10% figure): $12.90 − $1.29 = $11.61.

Tip on Pre-Tax or Post-Tax Total?

Etiquette guides are split, but the practical convention in the US is to tip on the pre-tax subtotal, since sales tax is a government charge unrelated to service quality. The difference is usually small — on a $100 bill with 8% sales tax, tipping 20% on $100 versus $108 is a $1.60 difference — but it adds up over many visits.

Splitting a Tip Is Not Always Splitting It Evenly

When a group splits a bill evenly, including the tip, the convention assumes everyone ordered roughly the same value of food. If one person ordered a $12 salad and another ordered a $45 steak with three cocktails, an even split of the tip means the salad-orderer subsidizes the steak-orderer's service tip. The mathematically "fair" approach is to tip proportionally to each person's own subtotal, then sum those individual tips — which produces the same total tip amount as a percentage of the full bill, just distributed differently across the group.

Use the USECALC Tip Calculator to compute the tip amount, total bill, and per-person split instantly — including uneven splits where each diner pays based on their own order.