How to Calculate a Tip (15%, 18%, 20%)

How to Calculate a Tip

Calculate a tip by multiplying the bill by the tip rate written as a decimal. For a 20% tip, multiply the bill by 0.20, so a 50-dollar bill gives a 10-dollar tip and a 60-dollar total. Change the decimal for a different rate: 15% is 0.15, 18% is 0.18, and 20% is 0.20. The tip is a percentage of the bill, and the bill plus the tip is the amount you pay.

A tip is one of the most common everyday percentage calculations, often done at the table without a pen. The Tip Calculator computes the tip and the split in one step. This guide covers the exact formula and the mental shortcuts for the standard 15, 18, and 20 percent rates.

The Tip Formula

The tip formula is Tip = Bill × (Rate ÷ 100), and the total is Total = Bill + Tip. The bill is the amount before the tip, the rate is the tip percentage, and dividing the rate by 100 turns it into a decimal. For an 18% tip on an 80-dollar bill, multiply 80 by 0.18 to get a 14.40-dollar tip, for a 94.40-dollar total.

This is the same percentage-of-a-number calculation used for discounts and tax, applied to a restaurant bill. The sibling guide on how to calculate a percentage of a number covers the general method. A tip is that method with the bill as the whole and the tip rate as the percentage.

The Quick 10% Method

The fastest way to tip uses 10% as a building block. Find 10% of the bill by moving the decimal point one place to the left, then combine it to reach the rate you want:

1. For 20%, double the 10% amount.
2. For 15%, add half of the 10% amount to itself.
3. For 18%, take 20% and subtract a small amount, or add 10% plus 8%.

On a 45-dollar bill, 10% is 4.50. Doubling gives a 9-dollar tip for 20%, and adding half of 4.50 gives a 6.75-dollar tip for 15%. This method needs no multiplication, because 10% is found by shifting the decimal, and the other rates are simple combinations of it.

Tip Chart for 15%, 18%, and 20%

The chart below shows the tip at the three standard rates for common bill amounts. Each column multiplies the bill by 0.15, 0.18, or 0.20.

Bill	15% tip	18% tip	20% tip
$20	$3.00	$3.60	$4.00
$40	$6.00	$7.20	$8.00
$50	$7.50	$9.00	$10.00
$75	$11.25	$13.50	$15.00
$100	$15.00	$18.00	$20.00

At a bill of 100 dollars, the tip in dollars equals the rate exactly, because 100 makes the percentage and the dollar amount the same number. This makes 100 a useful reference point: a 63-dollar bill sits a little above 60 percent of 100, so a 20% tip is a little above 12 dollars.

Worked Example: Tip and Total on a $64 Bill

Calculate an 18% tip on a 64-dollar restaurant bill, then the total.

1. Convert the rate: 18% becomes 0.18.
2. Multiply: 64 × 0.18 = 11.52, so the tip is 11.52 dollars.
3. Add: 64 + 11.52 = 75.52, so the total is 75.52 dollars.

Using the quick method as a check, 10% of 64 is 6.40, so 20% is 12.80 and 18% sits below that at 11.52. Both methods agree. Rounding the tip up to 12 dollars for a round 76-dollar total is common and gives a slightly higher rate.

How to Split a Tip Among People

Split a tip by calculating the total tip on the full bill first, then dividing the bill plus tip by the number of people. This gives an even split without each person tipping separately. On a 120-dollar bill with a 20% tip, the tip is 24 dollars and the total is 144 dollars.

Divide the 144-dollar total among 4 people to get 36 dollars each. Splitting after the tip is added keeps the arithmetic simple, and it ensures the full tip is covered rather than under-collected. The Tip Calculator does the tip and the per-person split together. The Percentage Calculator handles the underlying percentage if you want to see it.

Frequently Asked Questions

How do you calculate a tip?

Multiply the bill by the tip rate written as a decimal. For a 20% tip, multiply the bill by 0.20. On a 50-dollar bill, 50 times 0.20 equals a 10-dollar tip, for a 60-dollar total. To find a different rate, change the decimal: 15% is 0.15 and 18% is 0.18. The tip is the part, and the bill plus the tip is the total.

How do you calculate a 20% tip quickly?

Find 10% of the bill by moving the decimal point one place to the left, then double it. On a 45-dollar bill, 10% is 4.50, and doubling gives a 9-dollar tip for 20%. This shortcut avoids multiplying by 0.20 directly and works for any bill, because 20% is twice 10%.

How do you calculate a 15% tip?

Find 10% of the bill by moving the decimal one place left, then add half of that amount. On a 60-dollar bill, 10% is 6, and half of 6 is 3, so 6 plus 3 gives a 9-dollar tip for 15%. This works because 15% equals 10% plus 5%, and 5% is always half of 10%.

Should you tip on the pre-tax or post-tax total?

Tipping on the pre-tax subtotal is the common convention, because the tip rewards the service rather than the tax. Tipping on the post-tax total is also acceptable and gives a slightly larger tip. The difference is small on most bills, so either is reasonable; the pre-tax amount is the technically correct base for the service.

How do you split a tip among several people?

Calculate the total tip on the full bill first, then divide the total bill plus tip by the number of people for an even split. On a 120-dollar bill with a 20% tip of 24 dollars, the total is 144 dollars, and split among 4 people that is 36 dollars each. Splitting after adding the tip keeps the math simple and fair.