Money basics
How to Calculate a Tip: A Simple Formula, Examples, and Bill-Splitting Guide
Tip math is straightforward once you have one reliable formula. Use this guide for quick percentages, everyday restaurant bills, and splitting a total with friends.
Updated September 5, 2026 · 5 min read
The tip formula
The basic calculation is:
Tip amount = bill amount × tip percentage
Write the percentage as a decimal before multiplying. For example, 18% becomes 0.18 and 20% becomes 0.20. Add the tip amount back to the bill to get the final total.
15%, 18%, and 20% examples
Suppose the bill is $48.00. Here is what common percentage choices look like:
- 15%: $48 × 0.15 = $7.20 tip; final total $55.20.
- 18%: $48 × 0.18 = $8.64 tip; final total $56.64.
- 20%: $48 × 0.20 = $9.60 tip; final total $57.60.
There is no universal percentage that fits every place or situation. Check the bill for an included service charge, and choose an amount that makes sense for your local customs and experience.
Fast mental math
To estimate 20%, find 10% and double it. On a $48 bill, moving the decimal one place left gives $4.80; doubling it gives $9.60. For 15%, take 10% and add half of that amount: $4.80 + $2.40 = $7.20.
Rounding the bill first can make this easier. A $47.60 bill is close to $48, so a 20% tip is roughly $9.60. Use the exact total when you are ready to pay if precision matters.
How to split a bill with a tip
If everyone shared the bill evenly, add the tip before dividing. For a $96 bill with a 20% tip, the final total is $115.20. Four people would each pay $28.80.
When orders are different, a fairer approach is to calculate each person’s food and drink subtotal, apply the same percentage to each subtotal, then add the results. This also makes it easy to see whether tax, a service charge, or a shared item needs its own agreement.
Use a calculator when the bill gets complicated
A calculator is especially helpful for custom percentages, group bills, and uneven shares. Our Tip Calculator shows the tip, total, and per-person amount together so you can check the numbers before paying.
Frequently asked questions
How do I calculate a 20% tip quickly?
Move the decimal point in the bill one place to the left to find 10%, then double that amount. On a $48 bill, 10% is $4.80, so 20% is $9.60.
Do I calculate a tip before or after tax?
Local customs vary. If you have a preference, use the subtotal or total that matches it; the important part is being clear when splitting a group bill.
How do I split a bill with a tip?
Add the selected tip to the bill total, then divide by the number of people. If people ordered very different amounts, calculate each person’s share first and apply the same percentage to each share.
A quick reminder
This guide explains the arithmetic, not a rule for how much anyone should tip. Policies, service charges, and expectations vary by venue and location. Review the bill and make the choice that feels appropriate.