If it feels like your group spends more in summer, the data agrees, and the effect is bigger than you would guess. We looked at 4 million shared expenses logged on Banana Split over 13 years, sorted by the month they were actually spent. A third of a group’s yearly spending falls in July and August alone (32.7%, against 8.3% for an average month). August is the single busiest month of the year, and has been for a decade. But the summer bill is built in a specific way: not a few large purchases, but a flood of small shared costs.
What we measured, and what we did not
Banana Split has recorded its users’ shared expenses for more than ten years. For this article we took 4 million individual expenses dated between 2012 and 2025 and sorted them by the day they were spent, not the day the group was created.
Two honesty notes, because the numbers have to be readable. First, every euro figure is computed on groups settled in euros only: the raw data mixes currencies, and averaging across them would mean nothing. Second, we report medians, not averages. A handful of year-long events (shared flats, rolling budgets) pull the average up and would distort the picture of a typical trip. And as always, our users are people who chose an app to track their money, so the sample describes our groups faithfully, not all of humanity.
With that said, the pattern is one of the clearest we have ever seen.
A third of the year in two months
Sorted by the month each expense was actually spent, the year is anything but flat. Here is the share of a full year’s expenses that falls in each month, and the seasonal index (100 = an average month):
| Month | Share of expenses | Index (100 = average) |
|---|---|---|
| January | 6.3% | 75 |
| February | 5.9% | 71 |
| March | 5.9% | 71 |
| April | 5.8% | 69 |
| May | 6.9% | 83 |
| June | 8.4% | 101 |
| July | 14.9% | 179 |
| August | 17.8% | 214 |
| September | 8.0% | 95 |
| October | 6.9% | 83 |
| November | 5.7% | 69 |
| December | 7.5% | 90 |
August alone carries 17.8% of a year’s expenses, more than twice a normal month. Add July’s 14.9% and the two summer months hold 32.7% of everything a group spends in a year. The low point, November, sees barely a third of August’s volume. And it is not a fluke of one year: for the past decade, the busiest spending month has landed in July or August without a single exception.
This is not a quirk of our app either. Eurostat, in a report published in July 2026, found that 31.1% of all EU overnight stays in 2025 happened in those same two months, with 3.6 times more nights in August than in January. Our users, tracking their own money, reproduce Europe’s holiday calendar almost to the decimal.
Across 13 years of group expenses, which single month do groups spend the most in?
August is the busiest month of the year, holding 17.8% of all annual spending, more than twice an average month. July comes second at 14.9%. December, despite the holidays, sits below average because groups log fewer expenses then, even if each one is larger.
The August paradox: the most expenses, and the smallest
Here is the twist. August is the month with the most expenses, yet its average expense is the smallest of the whole year: about 106 EUR, against 356 EUR in December and 215 EUR in November.
Summer spending is granular. On a trip you log the groceries, the round of coffees, the ice creams, the parking, the beach chairs: dozens of small shared costs that each look trivial. December is the opposite, fewer expenses but big ones (gifts, the year-end dinner). The summer bill is heavy not because any single line is large, but because there are so many of them.
The typical summer group
Put together, the August group has a clear profile. It runs to a median of 10 logged expenses, against 7 the rest of the year, and spends a median of 687 EUR together, about 30% more than a group in any other month (528 EUR). It is also slightly smaller, three to four people, the shape of a bunch of friends on a trip rather than a household or a flat-share running all year.
More people, more moments, more small amounts to keep straight, and all of it exactly when everyone is relaxed and nobody wants to play accountant.
What it means for staying organized
The summer risk is not the size of any one expense, it is the volume. Thirty small costs are far easier to lose than three big ones, and that is where a group’s balance quietly tips onto whoever paid the most, a pattern we measured in detail: across 178,000 groups, one person usually fronts the majority of the money. Three habits keep an August trip clean.
1. Log on the spot. With a median of ten expenses per trip, memory is not a plan. Ten seconds at the table beats an evening of reconstruction at the end of the week.
2. Share the small stuff, not just the big bookings. The rental always gets remembered. The daily groceries and coffees, the ones that actually pile up in summer, are the ones that vanish. Our method for splitting travel expenses with friends covers both.
3. Settle as you go. A small front forgotten for three weeks becomes awkward; paid back the next day, it leaves no trace. The same habit applies well beyond holidays, in all the everyday situations where a group shares costs, from flat-shares to group dinners.
Keep summer counted
Summer is when groups spend the most, and in the most scattered way: a third of the year’s money, spread over dozens of small amounts, right when nobody feels like tracking it. That combination is exactly how a fair trip turns into a muddle at the airport on the way home.
Banana Split is free and keeps the running total for you: every expense logged in seconds, everyone sees who paid what in real time, and repayments are worked out automatically. You can download the app and set up your group in a minute, or first browse the expense-tracking features. This August, let the small stuff stay counted.