Two food budgets, one household
There are two versions of what you spend on food each month: the figure you would quote if someone asked, and the figure the actual transactions add up to. They are rarely the same, and the real one is usually larger, sometimes by half again. Not because anyone is careless. Spending is made of dozens of small, forgettable decisions, and human memory keeps the shape of things rather than the arithmetic.
A diary closes that gap in the only way that reliably works: by writing things down at the moment they happen, before the forgetting starts. That is the whole idea. Not budgeting, not optimising, not a system to follow. A record. The insight comes from the record existing at all.
Which also means a diary measures and does not change anything by itself. There is a real effect where recording spending reduces it slightly, purely through attention, but it is modest and it fades. If nothing changes as a result of what you learn, you have built an accurate record of a problem.
Five seconds or it dies
Type an amount, tap a category, add a note if you want one, and press add. The panel on the right totals the month and breaks it down by category, sorted by size, with the percentage each one takes. An entry is meant to take about five seconds, because tools in this category live or die on that number. People do not abandon spending trackers because the charts are wrong. They abandon them because logging a coffee felt like paperwork.
Log everything, though, or accept that you are sampling. Partial logging is worse than none: record the small purchases and forget the large occasional ones and your category breakdown will be confidently wrong, and you will draw conclusions from it. Categories themselves are a judgement rather than a fact (is a supermarket trip that included wine and cleaning products "groceries"?), so whatever you decide, decide it the same way every time, or your month-on-month comparison compares nothing.
Everything you enter is kept in this browser. Nothing is sent anywhere, no account is required, and no bank is ever connected; you cannot connect one even if you want to. Typing entries in is slower than automatic import, and it is also why there is no account access to grant, nothing to be breached, and no third-party aggregator holding your transaction history. The trade is fragility. Your entries survive closing the tab, but they will not follow you to another device, and clearing your browser site data deletes them. If you intend to keep a diary for more than a few weeks, an account, which fixes both, is the honest answer.
The three-month curve
The first week of a diary tells you almost nothing; you already knew roughly what you spent this week. The value arrives later, in a specific order. Somewhere in weeks two to four, the categories you underestimated appear. For most households that means eating out, groceries or small everyday transport: not the big obvious bills, which everyone already knows, but the accumulation of ordinary amounts nobody counts. Through months two and three, the shape of a normal month emerges, and with it the ability to tell a normal month from a bad one. This is where the diary stops being a chore and starts being useful. It is also the point most people never reach.
After that you can answer questions you previously guessed at. Is this month unusual, or is this just what months cost? The ONS family spending data makes a decent external yardstick for that question, if you want one. Did that change I made actually change anything? None of it requires a budget. A record is enough.
One caveat about early conclusions: one month is not a month. Nearly every household has irregular costs (annual insurance, car repairs, Christmas, a dentist) that skip a typical month and then arrive all at once, so a diary covering a quiet month will flatter you. Those lumpy costs are what the sinking funds planner exists to handle.
Where the free page ends
This page is one month, in one browser, with a fixed category list. It is genuinely useful on its own, there is no time limit on it, and it is free the way every calculator on FireMathLab is free. So is the account.
The full expense diary, which comes with that free account, adds the parts that only make sense once your data persists properly. Multiple accounts (current, cash, credit, savings), each with a running balance derived from an opening figure plus everything you have confirmed. Recurring bills and subscriptions, which post themselves on their due dates as pending entries for you to confirm, so the rent does not need typing every month. Safe-to-spend, your balances minus every bill due before your next income lands, which is the number people actually want and almost no banking app shows. Month-on-month trends and a 90-day projected balance. Transfers between your own accounts, correctly excluded from both income and spending. Your own categories, full history, and a JSON export of everything.
The dividing line is deliberate: the free page answers "where did this month go", and the account answers "what happens next". Getting those accounts and recurring bills set up takes a sitting, and the diary guide walks through that and the monthly reports waiting at the other end.
What the record feeds
A diary records what happened; three other tools here act on it. The payday allocator works in the opposite direction, deciding where money goes before the month starts rather than recording where it went, and diary first, then allocation, is the natural order: you cannot assign realistic amounts to categories you have never measured. The subscription audit covers recurring charges specifically, and is the faster route if that is all you want to look at. And the cash flow calendar maps when money moves within a month, a different question from how much. A month can balance perfectly and still bounce a payment on the 14th.
Last thing. This is a record-keeping tool and nothing here is financial advice: it reports what you entered, and what to do about it is yours to decide. For anything consequential, a regulated adviser is the right person to ask, and the FCA's consumer pages are a sensible place to start looking.