The formula is simple: tip = bill × tip percentage. Convert the percentage to a decimal before multiplying—18% becomes 0.18. Add the tip to the bill for the total, then divide by the number of people if the group is splitting evenly. The choices around that math vary by place, service, and circumstance; this guide focuses on calculating the amount accurately.

Fast mental math

  • 10%: move the decimal one place left. On $46.80, 10% is $4.68.
  • 20%: double 10%. On $46.80, 20% is $9.36.
  • 15%: add 10% and half of 10%. $4.68 + $2.34 = $7.02.
  • 18%: calculate 20%, then subtract 2%. $9.36 − $0.94 ≈ $8.42.

The Tip Calculator keeps the unrounded values through the calculation and rounds currency at the end, reducing the penny differences that can appear when each person rounds separately.

Before tax or after tax?

Both conventions exist. If a meal is $80 before tax and $86.40 after tax, a 20% tip is $16.00 on the pre-tax amount or $17.28 on the after-tax amount. The receipt may suggest percentages calculated one way or the other, so look at the base before accepting the printed number. A suggested amount is still voluntary when the customer can choose another amount or leave it blank.

Service charge, gratuity, or tip?

Read the receipt before adding anything. A mandatory service charge is not necessarily a tip distributed directly to the worker. The IRS distinguishes a voluntary tip—where the customer controls whether and how much to pay—from a compulsory service charge set by the business. If the receipt is unclear about where a charge goes, ask the business rather than assuming a second tip is required.

Splitting a bill

For an even split, calculate the tip on the full bill, add it, and divide once. Example: a $126 bill with an 18% tip produces $22.68 in tip and $148.68 total. Divided among four people, that is $37.17 each. If people ordered very different amounts, calculate each share of food and tax first, then apply the chosen percentage to each person's base. Assign any rounding penny to one person so the individual payments still equal the receipt total.

Choose the percentage in context

Tipping customs are not universal and change over time. The business model, local wage rules, type of service, group size, and an included charge all matter. A calculator should never present one percentage as a moral or legal requirement. When traveling, check current local guidance; in some countries adding a US-style percentage is unusual, while in others gratuity is expected.

Source

US tax distinction reviewed September 2026.