Tip Calculator Formula

Understand the math behind the tip calculator. Each variable explained with a worked example.

Use the Tip Calculator

Formulas Used

Tip Amount

tip_amount = bill_amount * tip_pct / 100

Total (Bill + Tip)

total = bill_amount + bill_amount * tip_pct / 100

Per Person

per_person = split > 0 ? (bill_amount + bill_amount * tip_pct / 100) / split : 0

Tip Per Person

tip_per_person = split > 0 ? (bill_amount * tip_pct / 100) / split : 0

Variables

VariableDescriptionDefault
bill_amountBill Amount(USD)85
tip_pctTip Percentage(%)18
splitSplit Between(people)2

How It Works

How to Calculate a Tip

Multiply the bill by the tip percentage, then divide by 100. On a $85 dinner, a 20% tip is $17. If splitting between 4 people, each person pays ($85 + $17) / 4 = $25.50. Most people round up for simplicity.

The Formula

Tip Amount = Bill x Tip Percentage / 100 Total Per Person = (Bill + Tip) / Number of People

Standard Tip Percentages (US)

  • 15%: Acceptable for average service
  • 18%: Standard for good service
  • 20%: Standard for great service, and increasingly the baseline expectation
  • 25%+: Above and beyond, for outstanding service or to account for small bills

    • These norms are US-specific. Many countries have no tipping culture (Japan, South Korea, most of Europe), and some include service in the bill. In the UK, 10-12.5% is common when tipping.

    Pre-Tax vs. Post-Tax

    Traditionally, you tip on the pre-tax amount. On a $100 meal with $8 in tax, a 20% tip should be $20 (not $21.60). In practice, most people tip on the total because it's easier to calculate. The difference is usually a dollar or two.

    When to Use This

    Restaurants, bars, delivery drivers, hair salons, taxi/rideshare, hotel housekeeping. For takeout, tipping is optional but 10-15% has become more common since 2020.

    Common Mistakes

  • Tipping on a bill that already includes a service charge or auto-gratuity. Check the receipt. Parties of 6+ often have an automatic 18-20% gratuity added.
  • Using the wrong base when splitting. If 4 people split a $200 bill with a $40 tip, each owes $60. But if one person ordered $100 of the $200, an even split isn't fair. Split by what each person ordered, then each adds their own tip.
  • Forgetting to tip on alcohol. Some people tip less on expensive bottles of wine. The standard is to tip on the full bill including drinks.

    • Worked Example

    An $85 bill with 18% tip split between 2 people.

    bill_amount = 85tip_pct = 18split = 2
    1. 01Tip = $85 x 0.18 = $15.30
    2. 02Total = $85 + $15.30 = $100.30
    3. 03Per person = $100.30 / 2 = $50.15
    4. 04Tip per person = $15.30 / 2 = $7.65

    Frequently Asked Questions

    How much should I tip?

    15% for adequate service, 18-20% for good service, 25%+ for excellent service. Many people now consider 20% the standard tip for sit-down restaurants.

    Should I tip on tax?

    Standard etiquette is to tip on the pre-tax amount. However, tipping on the total (including tax) is also common and appreciated, and the difference is usually small.

    How do I calculate a 20% tip quickly in my head?

    To find 20%, move the decimal point one place to the left (that gives you 10%), then double it. For example, on a $47 bill: 10% = $4.70, double it = $9.40. So a 20% tip is $9.40.

    Who should you tip and how much?

    Common tipping guidelines: restaurant servers 15-20%, bartenders $1-2 per drink or 15-20%, hotel housekeeping $2-5 per night, food delivery drivers 15-20% (minimum $3-5), taxi and rideshare drivers 15-20%, hair stylists 15-20%, and movers $20-50 per person depending on the job.

    Learn More

    Guide

    How to Calculate a Tip - Complete Tipping Guide

    Learn how to calculate a tip at restaurants, salons, and other services. Covers standard percentages, mental math shortcuts, and how to split the bill fairly.

    Ready to run the numbers?

    Open Tip Calculator