In the US, doubling the sales tax on the receipt gives a quick tip estimate.
US sales tax runs roughly 6–10% in most states, so doubling it lands close to the historical 15–20% tipping range — a genuinely fast mental-math shortcut, though it can undershoot the 18–20%+ baseline several 2026 etiquette guides now cite for ordinary good service.
Estimate with the rule, then check it against the calculator that models it properly.
Open Tip Calculator & Bill Splitter →