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Calculating road trip debts: Beyond the Excel Spreadsheet
December 25, 2009 7:44 AM   Subscribe

7 friends and I are going on a road trip. At restaurants we usually have one person pay by credit card, and have everyone paying for what they ordered to the individual. Oh, and not everyone is gonna be at every event, so having one individual pay for everything on the trip is impossible. And it should redistribute debts so at most each person only needs to make 1 payment to another person. What is the best free method for calculating who pays whom?

There are many websites, but the 5 or 6 I've tried so far all have at least one or more of the following problems:
1) Assumes that at restaurants everyone goes dutch and splits bills equally. (Not usually how my group does things; people will complain.)
2) Assumes that you are the person who pays for everything.
3) Limits free access to situations that have less than 8 individuals.
4) Does not optimize payments. (In theory, it should be possible to reassign debts from one individual to another so that each person only needs to make one payment to one person.)

Here is an simplified example:
4 people, 3 events...
*Person 1 paid for gas ($36), split among the three. Person 4 did not participate.
*Person 2 paid for a meal, where person 1's order was $6, person 2's was $8, and person 3's was $10. Person 4 did not participate.
*Person 4 borrowed $10 from Person 3.

I want to be able to plug how much each person owes at each event, who paid, and have it tell me something like:
Person 2 owes Person 1 $6.
Person 3 owes Person 1 $12.
Person 3 owes Person 2 $10, but since person 4 owes him $10, person 3 pays nothing and transfers the debt so...
Person 4 pays person 2 $10.
posted by jytsai to Grab Bag (18 answers total) 3 users marked this as a favorite
 
If you have a laptop use Excel or Google docs to set this up.

Else keep paper records.
posted by dfriedman at 7:54 AM on December 25, 2009


All this elaborate financial planning sounds antithetical to the whole idea -- the raison d'être -- of a road trip with friends. Wouldn't it be easier if you all just carried cash?
posted by M.C. Lo-Carb! at 8:01 AM on December 25, 2009 [1 favorite]


You can greatly simplify this by (initially) forgetting about who owes who, and instead just remember who owes and who is owed.

Every time a person pays, remember that, and the amount that they paid (but not for whom). Every time a person doesn't pay, remember that, and the amount they owe (but not to whom).

At the end, total each person's up individually, positive numbers for having paid and negative numbers for having owed. This will result in either a positive number or a negative number for each person; the people with negative numbers owe money to the people with positive numbers, and you can then easily work out an appropriate set of payments to zero everyone out.

You don't need a website. You need a piece of paper.
posted by Flunkie at 8:03 AM on December 25, 2009 [9 favorites]


Whenever a person pays they keep the receipt and write the person's name beside what they ordered. After the trip, individual's can tell each other person what they are owed.
posted by Midnight Rambler at 8:16 AM on December 25, 2009 [2 favorites]


Have you tried Buxfer?
posted by oinopaponton at 8:21 AM on December 25, 2009


This is pretty easy to do with this group travel ledger spreadsheet I've designed. The ledger keeps a running total of how much each person has contributed to the group expenses. There is a row for each transaction and a column for each member of the group. If an expense is shared equally by the group it is simply added to the member's column. If it's not, then it is offset by appropriate subtractions in the other members' columns, either individual amounts or you can simply divide equally if you are excluding one nonparticipant. This won't change the group total but will add credits and debits for the appropriate people.

At the end, you are left with a figure for uncredited group expenses that is divided equally per person, converted into another currency if necessary. The amount they are in credit to the group is subtracted from this quantity, leaving the amount that they owe the group, or are owed by the group. Figuring out how to make the settlement transactions at that point is up to you.

You can leave a bunch of empty spaces and print it out for scribbling while on the road.
posted by grouse at 8:27 AM on December 25, 2009


I've got to agree with M.C.... you're not going on a road trip, you're living a frustrating math story problem....

Carry cash, pay your share, you'll have fewer arguments and bad feelings....
posted by HuronBob at 8:31 AM on December 25, 2009


What you want is billshare. It does pretty much everything you want. You just need to enter everyone's email address. From there, you create a group and add your receipts. You can assign amounts, settle debts, etc. My roommates and I used it heavily, and it's pretty much amazing.
posted by runningwithscissors at 8:39 AM on December 25, 2009


I'm going to be more explicit about the method I suggest. Take your example:
Here is an simplified example:
4 people, 3 events...
*Person 1 paid for gas ($36), split among the three. Person 4 did not participate.
*Person 2 paid for a meal, where person 1's order was $6, person 2's was $8, and person 3's was $10. Person 4 did not participate.
*Person 4 borrowed $10 from Person 3.
The method I suggest, applied to this example:

Everybody starts at 0.

Event 1: Person 1 pays 36 but "owes" 12 (of that 36), for a total of being owed 24. Person 2 owes 12; so does Person 3. Totals are now:Event 2: Person 1 owes 6; Person 2 is owed 16; Person 3 owes 10. Totals are now:Event 3: Person 3 is owed 10; Person 4 owes 10. Final totals:And then just zero everyone out. For example, Person 3 gives twelve bucks to Person 1, and Person 4 gives six bucks to Person 1 and four bucks to Person 2.
posted by Flunkie at 8:50 AM on December 25, 2009 [4 favorites]


And just to show you that this method really works, and that everything adds up appropriately:

Person 1 spent $36 in cash, and got $12 of gas, $6 of food, and $18 of cash - i.e. zero total.

Person 2 spent $24 in cash, and got $12 of gas, $8 of food, and $4 of cash - i.e. zero total.

Person 3 spent $22 in cash, and got $12 of gas and $10 of food - i.e. zero total.

Person 4 spent $10 in cash, and got $10 in cash - i.e. zero total.
posted by Flunkie at 8:56 AM on December 25, 2009 [1 favorite]


Write down who paid what and then let Billmonk handle who owes who.
posted by Idle Curiosity at 9:27 AM on December 25, 2009 [2 favorites]


Billmonk is great for this.
posted by soleiluna at 9:46 AM on December 25, 2009 [1 favorite]


Do what Flunkie says, it's somewhat counterintuitive but it works. Essentialy, you are setting up a big pot for common expenses, starting out at zero. Everybody just holds a scorecard, and keeps track of what they consume / contribute to the common pot, the people owing money don't need to know specifically who they owe to.

If you think the last step is confusing, just use a big bag-O-money! If someone has a negative total, they put money in the bag. If they have a positive total, they take money from the bag. Everyone will be happy at the end, with zero hassle.
posted by Dr Dracator at 10:20 AM on December 25, 2009


when my friends went on a road trip we decided we would throw X amount into a general fund that we used for meals, food for the group and gas. then we went to the bank and got Visa gift cards with the general fund money -- that way we didn't have to keep track of any receipts.

then when we got back we bought a keg with the left over money on the gift cards :-)
posted by nanhey at 11:33 AM on December 25, 2009 [1 favorite]


I think you should take Flunkie with you.
posted by Kangaroo at 4:55 PM on December 25, 2009


Beware of people calculating what they owe at a restaurant. They tend to short either the tax or the tip, leaving the payer overpaying.
posted by musofire at 8:00 PM on December 25, 2009


I use Billmonk.com and it works beautifully for any number of participants/payees/individual or split checks/ etc.

+1 musofire
>> Beware of people calculating what they owe at a restaurant. They tend to short either the tax or the tip, leaving the payer overpaying.

This happens all the time. Billmonk has two fields for tax and tip and it calculates each person's shared based upon their participation.

Its free and I have been using it for almost 3 years now.
posted by bbyboi at 8:15 PM on December 25, 2009


Kangaroo is joking, I think, but Flunkie's approach really does require that you have a Designated Flunkie with you. You need one and only one person, call him the DF, who will be making all the calculations. Otherwise you're stuck trying to do math by committee and that leads to anger and an increased error rate.

What's more, your DF needs to be someone who is trusted by the entire group to be impeccably honest and make flawless calculations. Otherwise Friend #2 will pipe up saying "I'm not so sure about X," and then Friend #3 will step in to explain it to him, and Friend #4 will correct Friend #3's explanation, and now you're right back to math-by-committee and you all hate each other's guts.

I've known a few groups of people where there was a natural DF — a born calculator with good morals and an anal-retentive streak who was always getting called on to figure out tips and help people with their taxes and whatnot. Such a person can carry out the calculations that Flunkie is recommending without stirring up suspicion, confusion or animosity. But if your party lacks such a person — or, just as bad, if you have two — you should really go with Billmonk instead, because the piece-of-paper solution, while technically "simpler," will end in tears.
posted by nebulawindphone at 8:26 PM on December 25, 2009


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