Weighted Bill Split Calculator

What is a weighted bill splitter?

A calculator for splitting a restaurant or group bill when an even split isn't fair — someone ordered drinks, someone skipped dessert, or one person is covering less than everyone else. Give each person a weight instead of dividing by headcount, and it rounds the result to cash you can actually hand over, putting the leftover cents on one person so the total always matches the receipt exactly.

How do I use it?

1. Enter the total bill amount
2. Add a participant per person and give each one a weight (0.1 to 10, in steps of 0.1)
3. Pick a rounding amount and who absorbs the leftover
4. Press Split the bill for a per-person amount, then Copy breakdown to paste it into a message

What's the actual formula for a weighted split?

Each person's share is total × their weight ÷ everyone's weights added together, then rounded down to the chosen amount (never up). Rounding down on every share means the shares added together fall a little short of the total; that shortfall gets added to whichever person the "who covers the remainder" setting points to, so the shares always add back up to the exact bill.

For example, a 90 bill split between someone who ordered extra (weight 1.5), a standard share (1.0), and someone who ordered less (0.7) — weights adding to 3.2, rounded to the nearest $5, remainder to whoever weighs the most — comes out to:

That adds up to 90, matching the bill exactly. The rounded-down shares alone come to 80, and the 10difference is added to whoever ordered extra.

When does a remainder show up, and when doesn't it?

Whether a remainder appears depends on whether the total divides evenly, not on the tool:

• Remainder example: 100 split three ways with no weighting, rounded to the nearest $20 — each theoretical share (about $33) rounds down to 20, leaving a 40 shortfall that goes to the organizer, who ends up with 60 while the other two pay 20 each
• Even split: 90 split three ways at the nearest $10 divides exactly (each theoretical share is already a multiple of $10), so everyone pays 30 with no remainder
• No rounding ($1): 100 split three ways with rounding off comes to 33 for two people and 34 for the organizer, who picks up the1 remainder

Which rounding amount should I pick?

Match it to how you're settling up. Paying through an app where exact change costs nothing? Use $1 (no rounding). Splitting cash and want to hand over whole bills instead of counting singles? Nearest $5 is the useful middle ground, andnearest $10 or $20 work for a bill large enough that a few dollars of rounding doesn't matter to anyone.

The bigger the rounding amount, the bigger the gap between most people's share and whoever covers the remainder. Splitting 685 between 7 people with no weighting shows the pattern:

At $1 rounding the gap is small — 103 versus 97. By $20 rounding it has grown to 205 versus 80 — the remainder-bearer is paying more than double. If a wide gap would bother the group, pick a smaller rounding amount rather than a larger one.

Who should cover the rounding difference?

There's no fixed convention, so this tool offers both options this site has seen used in practice. The organizer puts it on whoever is first on the list (typically whoever is organizing and already handling the logistics); the person paying the most puts it on whoever has the highest weight, on the reasoning that someone already paying more absorbs a small amount easier than someone paying less.

How much extra should someone who ordered more actually pay?

There's no fixed rule — the weight field takes any value in steps of 0.1. A common range in practice is 1.3–1.5× for someone who ordered noticeably more (extra drinks, a bigger entrée) and 0.6–0.8× for someone who ordered less or skipped a round, with 1.0× as the standard share. Setting every weight to 1.0 gives a plain even split.

Can this handle someone who joined late or left early?

Not directly — weight is a proportional adjustment to one bill, not a way to mark someone as partially present. The reliable approach for a two-part night (dinner, then drinks after) is to split each part's total separately with only the people who were there, then add the two results per person. For someone who just wants a lighter share rather than an exact itemization, a lower weight (0.5–0.7) approximates it without being a precise per-item split.

Someone already paid the whole bill upfront — can this help split the reimbursement?

Yes, in two steps. First, run the bill through this tool as normal to get each person's share. Then have everyone pay their share to whoever covered the bill, instead of paying the restaurant directly. The tool works out who owes what; moving the money is a separate, manual step.

What amount do I enter if there's a discount or coupon?

The amount actually charged, after the discount. If a 60 bill has a 10 coupon applied, enter 50. To give the person who brought the coupon a lighter share, lower their weight rather than trying to subtract the discount from their portion by hand.

Notes

• Rounding always rounds down, never up — the remainder is added on top, so nobody pays less than their rounded-down share
• Total amount: 1 to 100,000,000. Participants: 1 to 100. Weight: any number greater than 0
• Weight is a free-form multiplier in steps of 0.1; the 1.5 / 1.0 / 0.7 figures above are common starting points, not fixed values
• Nothing you enter is sent anywhere — the split runs in your browser and disappears on reload unless you copy the breakdown first