How to build a shared budget spreadsheet for two people
· 8 min read
A shared budget spreadsheet needs four columns, one SUMIF formula, and an agreement about who updates it. The columns are what, how much, who paid, and when it repeats. The formula works out how much each person has actually put in. The agreement is the part everybody skips, and it is the part that decides whether the file is still being used in March.
The four columns you actually need
Most shared budget sheets start with about eleven columns and lose three of them to neglect within a month. Four is enough to answer every question a household actually asks.
- Item. What the money is for, in the words you would use out loud. Rent, power, the weekly shop.
- Amount. One number, no currency symbol typed by hand, formatted as currency by the column rather than by you.
- Paid by. A name, spelled the same way every single time. This column is what every formula below depends on, so a stray 'alex' with a lowercase a will quietly break your totals.
- Repeats. Monthly, yearly, or blank for a one-off. This is the column people leave out and then rebuild in January when they cannot remember which rows were annual.
Use a dropdown for 'Paid by' rather than free text. In Google Sheets that is Data, then Data validation, then a list of the two names. It takes forty seconds and removes the single most common cause of a broken shared budget.
The formula that does the real work
With those columns in place, the question 'how much has each of us actually paid this month' is one formula. If your items run from row 2 to row 40, with amounts in column B and names in column C:
=SUMIF($C$2:$C$40, "Alex", $B$2:$B$40)
The dollar signs matter. They lock the range so that copying the formula into the cell next to it, and changing only the name, gives you the second person's total instead of silently sliding the range down four rows. That single detail is the difference between a sheet that stays right and one that starts producing numbers nobody trusts.
Adding a proportional split
If you have decided to split by income rather than down the middle, put both take-home figures somewhere out of the way, say F2 and F3, and work out each person's share of the household income once:
=$F$2/($F$2+$F$3)
Multiply the shared total by that number and you have what one person's fair share comes to. Compare it against what they actually paid, and the difference is what settling up would cost. Two cells, and it answers the question most couples end up guessing at.
The proportional split formula in fullA separate post walks through the whole thing with a worked example, including what to do when one income is irregular and the three ways this particular formula tends to break.The bills that repeat, which is most of them
Rent, insurance, the phone contract and every subscription behave the same way every month, which makes retyping them a strange thing to do twelve times a year. The usual fix is one tab per month, copied from the last one. It works, and it has a cost worth knowing about in advance: any formula that reaches across tabs breaks the moment somebody renames one, and every correction has to be made in the current tab and then remembered for the next copy.
The alternative is a single sheet with the Repeats column doing the work, and a total that filters rather than copies. Harder to set up, much less to maintain.
The rule that matters more than any of this
Decide, out loud, who adds things and when. Not because one person should own it, but because 'whoever gets to it' reliably resolves to one person within about six weeks, and the other one gradually stops opening the file. At that point the household has a budget that one of them can see, which is a different and much less useful thing than a shared one.
- Pick a moment rather than a person. Sunday evening, or the day the rent leaves. A time is easier to keep than a duty.
- Agree what does not go in. Most sheets die of ambition. If a coffee does not need to be in there, say so on day one.
- Put the renewal date next to anything that renews. It is the only column that warns you about something before it happens.
When a spreadsheet stops being the right tool
A spreadsheet is genuinely good at this, right up to the point where two people need it on two phones. Editing a wide sheet on a phone is unpleasant enough that most people stop doing it, which is how the file ends up six weeks out of date without anybody deciding to abandon it.
The same four columns, on two phonesPairly is what we built when our own spreadsheet reached that point. The same information, typed once, with the split worked out and the same month visible to both people. No bank connection: you decide what goes in, exactly like a spreadsheet.One picture, two accounts, no bank login.
Pairly is for people who share the bills and not the account. Set up a month in two minutes and see what it looks like.