How to Calculate a Tip Before or After Tax

The two numbers on your receipt

The subtotal is the price of the food and drinks you ordered. The total adds state and local sales tax on top. Tax is not part of the service your server provided, so the traditional etiquette is to tip on the subtotal. Many people still tip on the total simply because it is the easiest number to find, and that is perfectly acceptable too.

Method 1: tip before tax

Multiply the subtotal by your tip rate, then add both the tax and the tip.

Tip = subtotal × tip % · Final total = subtotal + tax + tip

Method 2: tip after tax

Add the tax first, then multiply that full amount by your tip rate.

Tip = (subtotal + tax) × tip % · Final total = subtotal + tax + tip

Worked example: an $80 dinner with 8% tax

Two people share dinner. The subtotal is $80.00 and sales tax at 8% adds $6.40, so the receipt total is $86.40. They want to leave 20%.

The gap is always the tax amount multiplied by the tip rate — here $6.40 × 20% = $1.28. On everyday meals it is small; on a $600 group dinner in a city with 10% tax at a 20% tip it grows to $12.

Mental-math shortcuts

• 10%: move the decimal one place left. $80.00 becomes $8.00.
• 20%: double the 10% figure. $8.00 × 2 = $16.00.
• 15%: take 10% and add half of it. $8.00 + $4.00 = $12.00.
• 18%: take 20% and subtract 2% (one fifth of 10%). $16.00 − $1.60 = $14.40.

Which method should you choose?

Tip before tax if you want to follow the traditional rule or you are watching a budget on a large bill. Tip after tax if you prefer a quick calculation from the bottom line, or if you simply want to be a little more generous. Either choice is considered polite in the United States — the percentage you pick matters far more than the base you apply it to.

Watch for these on the receipt

• Discounts and coupons: tip on the price before the discount, since the server did the same amount of work.
• Suggested tip lines: check whether the printed suggestions are based on the subtotal or the total. Some point-of-sale systems use the after-tax amount.
• Service charges: if a gratuity or service charge is already listed, you do not need to add a full tip on top.