One formula, no hiding place
Everything you own minus everything you owe. That is the whole formula, and its usefulness comes from what it refuses to hide: a pay rise that all goes out again does not move it, and neither does a bigger house bought with a bigger mortgage.
Four things belong on the asset side (cash, investments, pensions, and property), and everything borrowed belongs on the other. Two entries deserve scrutiny before you type them in. Your home is a legitimate asset, so include it for a complete picture, but keep it separate in your head when planning retirement: a home cannot fund your retirement while you live in it, it cannot pay your grocery bill, and that is exactly why the FIRE calculator and the other FIRE tools here exclude it by default. Your pension is the opposite case, often the largest number most people never look at even though workplace auto-enrolment has quietly built one for almost every employee, and leaving it out makes progress look far worse than it is. The car earns a line only if it is worth enough to matter and you would actually sell it; depreciating items add noise, and most people leave them out. Bear in mind, too, that property and pension values are estimates. Both are illiquid and updated infrequently, and refreshing a house valuation monthly manufactures noise. Once or twice a year is plenty.
On its own the total is nearly meaningless. Nobody's £180,000 tells you whether they are doing well; £180,000 that was £164,000 six months ago tells you a great deal. Net worth is a derivative measurement: the value is in the slope, not the level. Which is also why a negative figure is not a failure. It is the normal starting point after a mortgage or student loan, the trend is what matters, and the debt payoff planner shows how fast the negative side shrinks under a given plan.
The case for once a month
Check daily and you are mostly watching markets, which move for reasons that have nothing to do with your decisions. Check yearly and you get twelve months of drift before you notice a problem. Monthly is the interval where your own behaviour (what you saved, what you repaid) is large enough to see against the noise.
How the check-ins work in the app, and how to read the rings and trend charts they build up, is the subject of the tracker guide.
A month is also short enough to remember. When you log the number and write "car repair" or "bonus paid" beside it, you build something no bank feed produces: a record of why the line moved. Twelve of those notes explain a year better than any chart.
And the bank feed is missing on purpose. Linking accounts means handing credentials and a permanent read of your transactions to a third party; typing six numbers once a month takes four minutes and keeps the data yours. That trade is the whole design philosophy here. One consequence of the manual approach: multi-currency holdings are converted for display at approximate static rates, so cross-currency totals drift from spot.
Tom's March
Tom's first three check-ins, entered by hand in about four minutes each:
| Month | Assets | Debts | Net worth | Change |
|---|---|---|---|---|
| January | £431,000 | £220,400 | £210,600 | — |
| February | £436,200 | £219,100 | £217,100 | +£6,500 |
| March | £433,900 | £217,800 | £216,100 | −£1,000 |
March looks like a bad month and was not. His mortgage fell another £1,300, repayment continuing exactly as designed, while his investments dropped £2,300 on a market wobble that reversed in April. The only figure under his control moved the right way.
That distinction is what a monthly series gives you: the ability to separate what you did from what the market did. Judged on the first, March was a good month.
What the slope cannot tell you
A rising line is not a complete verdict. Net worth says nothing about cash flow, so a high total with no accessible savings is a real and uncomfortable position the number alone will never warn you about. Investments and property also carry a future tax bill on their gains that never appears on the asset line, which flatters the total slightly every month.
And resist grading yourself against other people. Age benchmarks hide enormous variation in property, inheritance and pension access, a spread the ONS's income and wealth statistics document at national scale; net worth by age explains why the medians deceive. The one comparison this tracker is built for is you, against last month.