A month is not four weeks, and that is where the money goes
It is 4.333 weeks. Multiplying a weekly cost by four to get a monthly one charges you for 48 weeks a year and quietly loses the other four.
On a £90 a week food shop that is £360 a year of spending that genuinely happens, leaves the account, and is nowhere in the budget. Add a £40 a week petrol habit and it is £520. That is most of the answer to "where does it all go" before anything else has been looked at.
The correct conversion is weekly times 52 divided by 12. Everything here is converted that way, and the tool shows what the shortcut would have cost you rather than fixing it silently, because the number is the point.
Being paid four-weekly is not being paid monthly
Four-weekly pay is thirteen packets a year. Your rent, council tax and direct debits go out twelve times. Those two facts do not reconcile, and no monthly budget can describe what is happening in the account.
In practice, payday drifts earlier through the year, two months end up with a payday landing at an awkward point, and one month has two paydays in it. That last one feels like a good month and is not: it is the month before that was short, arriving late.
The number that keeps the account straight is what has to come out of each packet, which is the annual total divided by thirteen rather than by twelve. The tool shows that figure alongside the monthly one so you can budget on the one you are paid on.
The annual costs are the ones that break it
This is the most common failure and it is entirely structural. A budget built by looking at one month of bank statements contains everything that happened in that month, and nothing that did not.
Car insurance. MOT. The service. The TV licence. The boiler service. Christmas. Birthdays. The holiday. The dentist. Every one of those is real, recurring and predictable, and none of them is monthly. A quiet month contains none of them, so the budget balances, and then March arrives.
Enter them here at their own frequency. The tool works out what they come to a month and shows that figure separately, because it is money that has to be set aside rather than money that is spare. That one line is usually the difference between a budget that works and a budget that looks like it works.
50/30/20, applied to the right number
Fifty per cent on needs, thirty on wants, twenty on saving and debt. It is a reasonable rough shape and two things routinely go wrong with it.
It is meant for take-home pay, and it gets applied to gross constantly, which flatters everybody by roughly the size of their tax bill. If the percentages look comfortable, check which figure they were worked out against.
And the twenty includes debt repayment, not just saving. Overpaying a credit card at 22% is a better use of that slice than a savings account paying 4%, and it counts towards the same target. Plenty of people think they are failing the rule because they are paying down debt instead of saving, when they are doing exactly what it describes.
Enter everything at the frequency you pay it
It feels like extra work and it is the opposite. Do not convert anything before you type it in. Weekly stays weekly, quarterly stays quarterly, annual stays annual.
The conversion is where it goes wrong, so doing it yourself in your head before entering it is exactly the step this is meant to remove. Every line shows what it comes to a month next to it, so you can see the arithmetic happening rather than trusting it.
Where this is saved, and what that means
In your browser, on this device, and only when you press save. There is no account, nothing is uploaded and nobody else can see it. Every tool on this site works this way, and a budget is exactly the kind of thing it matters for.
The trade-off is real and worth stating. Clearing your browser data clears this with it, private browsing will refuse to save at all, and it will not follow you to your phone. If these numbers matter to you, keep a copy somewhere else as well.
Common questions
How do I convert a weekly cost to a monthly one?
Multiply by 52 and divide by 12, which gives 4.333 weeks. Multiplying by four is the common shortcut and it charges you for 48 weeks a year, losing the other four entirely. On a £90 a week food shop that is £360 a year of real spending that appears nowhere in the budget.
I am paid four-weekly. Why does my budget never work?
Because four-weekly pay is thirteen packets a year, not twelve, while your rent and direct debits go out twelve times. The monthly figure never describes an actual month. Two months a year have a payday that lands early and one has two paydays in it, which is the month that feels flush and the one after that does not. Budget on what has to come out of each packet instead.
Why does my budget balance but I still run out of money?
Almost always the annual costs. Car insurance, MOT, service, TV licence, boiler service, Christmas, birthdays, dentist. A budget built from one month of bank statements contains none of them, because none of them happened that month. They are real, and the money has to come from somewhere.
What is the 50/30/20 rule and am I applying it right?
Fifty per cent on needs, thirty on wants, twenty on saving and debt. Two things get it wrong. It is meant to be applied to take-home pay and it is routinely applied to gross, which makes everybody look better than they are. And the twenty covers debt repayment as well as saving, so paying down a card counts towards it rather than sitting outside it.
Where is my budget saved?
In your browser on this device, and only when you press save. There is no account, nothing is uploaded, and nobody else can see it. The flip side is that clearing your browser data clears it too, and it will not follow you to another device. If the numbers matter, write them down somewhere as well.
Should I enter everything as a monthly figure?
No, enter each thing at the frequency you pay it. The conversion is exactly where budgets go wrong, so doing it yourself before you type it in defeats the point. Weekly stays weekly, annual stays annual, and the tool does the arithmetic properly and shows you what each one comes to a month.