How to split tax and tip fairly (and why not evenly)

When a group splits a restaurant bill by item, tax and tip are where it usually goes wrong. People split the food carefully, then divide the tax and tip evenly “to keep it simple”. It feels fair, but it quietly charges whoever ordered the least for part of everyone else’s meal.

Why not split tax and tip evenly?

Jordan had a $9 soup, Casey a $26 pasta and Riley a $45 ribeye. With 8% tax ($6.40) and a 20% tip ($16.00), the bill is $102.40. Here’s what each person pays when the food is split by item and the tax and tip are split two different ways:

	Food	Tax & tip split evenly	Tax & tip in proportion
Jordan	$9.00	$16.47	$11.52
Casey	$26.00	$33.47	$33.28
Riley	$45.00	$52.46	$57.60
Total	$80.00	$102.40	$102.40

Split evenly, Jordan pays $4.95 more than their fair share - 43% more - while Riley pays $5.14 less. Most of the tax and tip came from Riley’s ribeye, so Riley’s share of both should be the biggest.

How to split tax and tip in proportion

1. Work out each person’s food total. Add up what they ordered, including their part of anything shared.
2. Find each person’s share of the subtotal. Divide their food total by the subtotal. Jordan’s $9 of an $80 subtotal is 11.25%.
3. Give them that share of the tax and the tip. Jordan pays 11.25% of $6.40 in tax ($0.72) and 11.25% of $16.00 in tip ($1.80).

As a formula:

Person’s tax and tip = (tax + tip) × (their food ÷ subtotal)

	Food	Share	Tax	Tip	Total
Jordan	$9.00	11.25%	$0.72	$1.80	$11.52
Casey	$26.00	32.5%	$2.08	$5.20	$33.28
Riley	$45.00	56.25%	$3.60	$9.00	$57.60
Total	$80.00	100%	$6.40	$16.00	$102.40

The one-number shortcut

Add the tax and tip together and divide by the subtotal: $22.40 ÷ $80.00 = 28%. Now everyone simply pays 1.28 × their food:

• Jordan: $9.00 × 1.28 = $11.52
• Casey: $26.00 × 1.28 = $33.28
• Riley: $45.00 × 1.28 = $57.60

Same answer as the table, with one multiplication each. It works for any bill: work out (tax + tip) ÷ subtotal once, and multiply everyone’s food by 1 plus that.

Should the tip be on the subtotal or the total?

Both are common. Many people tip on the subtotal (before tax); tipping on the total (with tax) is a little more generous: on this bill, 20% of $80.00 is $16.00, while 20% of $86.40 is $17.28 - a $1.28 difference.

It doesn’t change how you split it. Whichever tip you leave, divide it in proportion to what each person ordered.

Service charges, fees and discounts

• Automatic gratuity or service charge: treat it like a tip and split it in proportion.
• Discount or coupon: split it in proportion too, in reverse - it comes off each person’s total by their share of the food.
• Rounding: each person’s share usually has a fraction of a cent. If the rounded totals come out a cent off the bill, give that cent to one person. The restaurant bill guide shows a real example.

When is splitting evenly fine?

When everyone ordered about the same, the difference is pennies. Two people with $30 and $34 meals would be off by well under a dollar, and many groups happily round that away. The proportional split matters when orders are noticeably different - one person had soup, another had the steak.

Let something else do the math

The free split bill calculator splits tax and tip this way as you type - add who had what, then the tax and tip. Or scan the receipt with PayMate and it reads the items, tax and tip for you, then splits everything in proportion down to the cent.