"Where did it all go?" is the most common money question and the easiest one to answer badly. Bank statements are noise. Spreadsheets die by February. The trick is to get spending insights from data you're alreadyentering — and if you split expenses with friends or roommates, you already are. Here's how to track monthly spending and actually understand it.
The two numbers that matter
For anyone who shares expenses, "how much did I spend" is really two questions:
- Personal spending — things you bought just for yourself.
- Your share of shared expenses — not what you fronted for the group, but the slice that was actually yours.
Most tools conflate these. If you paid a $300 group dinner, your card statement says you spent $300 — but if friends owe you $225 of it, your real cost was $75. BillBuddies' Insights page separates the two and totals them correctly, so the monthly number reflects reality.
Reading the by-category breakdown
Insights breaks the month down by category — food, transport, entertainment, utilities — with personal and shared portions shown separately. Patterns show up fast:
- A food category that's 80% "shared" means group dinners, not groceries.
- A transport spike in one month usually maps to one trip — check the group.
- Categories with a budget set show status against the limit, so the breakdown doubles as a budget report.
Use the 6-month trend, not the single month
Any individual month lies. Your birthday month is high; the month you were sick is low. Insights shows a rolling 6-month trend so you can tell the difference between a blip and a drift. The question to ask isn't "was this month high?" but "is the trend line climbing?" A category creeping up 10% month over month for half a year is a habit change you haven't noticed yet.
A 10-minute monthly review
Once a month, ideally right after you settle up with friends:
- 1. Check the total — personal + your shared share. Is it inside the range of the last six months?
- 2. Scan categories— anything at 100%+ of budget, or wildly off its usual level? Open it and look at the actual expenses. Usually it's two or three big items, not a hundred small ones.
- 3. Look at the trend— any category rising three months in a row gets a budget (or a decision to accept it — that's allowed too).
- 4. Settle up — clear balances with friends so next month starts clean. Our settling-up guide covers this.
Why this works when budgeting apps don't
Dedicated budgeting apps fail for one reason: the data entry is a chore that serves no immediate purpose, so it stops. In an expense-splitting app, logging is the point — you do it so your friends pay you back. The insights are a by-product of a habit you keep for social reasons, which is the only kind of habit that survives. Log the expense once, split it, and the analysis builds itself.