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Restaurant tip

How to calculate a restaurant tip without slowing the table down

Calculate a 15–25% tip in your head, before the card reader reaches the table.

Tipping is the percentage calculation people do most often without consciously realising they are doing math. The standard 15–20% has the convenient property that you can build it from 10% — a single decimal shift — and tack on half or all again to reach 15% or 20%. With a little practice the whole thing happens before the server returns with the card terminal.

This guide walks the formula, then offers the mental-math habits that make the bill math feel automatic.

Calculating a 18% tip

For a $72 bill at 18%, the math is the same percent-of-a-number you use for tax:

  • Tip amount: $72 × 0.18 = $12.96.
  • Total with tip: $72 + $12.96 = $84.96.

Tipping customs differ by country and venue. Always decide ahead of time whether you tip on the pretax subtotal or the post-tax total so groups stay in sync.

Tip table for $72

The same $72 subtotal under different percentage settings, so you can scan instead of recompute.

Percent Tip amount Grand total
10%$7.2$79.2
12%$8.64$80.64
15%$10.8$82.8
18%$12.96$84.96
20%$14.4$86.4
22%$15.84$87.84
25%$18$90

The 10% mental-math trick that powers every tip

Every common tip percentage is a small adjustment to 10%, which you can find by shifting the decimal one place to the left:

  • 15% tip: take 10%, then add half of it. A $72 bill → 10% is $7.20, half of that is $3.60, total $10.80.
  • 18% tip: take 10%, double it (20%), drop 2% (a fifth of 10%). $14.40 − $1.44 = $12.96.
  • 20% tip: double 10%.
  • 25% tip: add 10% + 10% + 5% (half of 10%).

None of these need a phone. The whole calculation happens in 5 seconds with a little practice.

Common mistakes to avoid

  • Stacking discounts by addition. 20% off plus another 10% applied to the lowered price is roughly 28% off the original, not 30%.
  • Tipping on the post-tax total without realising the venue intended pretax.
  • Treating "tax-free weekend" as universal — eligible product lists still apply.
  • Forgetting that loyalty rewards may calculate on post-discount spend, not the sticker price.

Calculation tips & best practices

  • Note the discount order from the receipt: percent off first, then dollar coupons, then tax.
  • Tipping mental shortcut: take 10% (decimal shift) and adjust from there.
  • When comparing two stores, always compare the after-tax, after-discount total.
  • Screenshot a confusing shelf tag and recompute later — fewer mistakes than rushing at the till.

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Note: Percentage results are estimates for informational use only. Always verify critical financial, tax, or business calculations with a qualified professional.

Calculate the tip and bill total

Switch the calculator to Increase mode, enter the bill total and the tip percentage, and the calculator shows the tip and the grand total side-by-side.

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