Net worth is assets minus liabilities. It is the best single number in personal finance because it is the only one that cannot be improved by moving money between your own accounts. Paying a credit card from savings leaves it unchanged, which is exactly right — nothing about your position changed.
That same property is what makes it incomplete. A single figure that treats every dollar as interchangeable is silent on four things that decide what you can actually do.
One: how much of it you could spend this week
A house, a retirement account, and a checking balance can add to the same total and behave nothing alike. One takes months to convert and costs several percent to sell. One converts in days and may cost a penalty and a tax bill. One converts instantly.
Net worth going up while liquid savings goes down is a real and common pattern — it is what buying a house looks like, and what an aggressive extra mortgage payment looks like. Neither is a mistake. But the total will not tell you that the month got tighter, and the month did.
Track a liquidity figure alongside the total: cash and cash-equivalents, nothing else. It answers the question net worth cannot, which is what happens if income stops for ninety days.
Two: how old the numbers are
Every net worth figure is a mix of values measured at different moments. A checking balance is from this morning. A brokerage balance is from the last close. A house valuation is from whenever somebody last estimated it, and a car's is from a depreciation table.
This is unavoidable and mostly harmless, with one exception: illiquid estimates tend to be updated only when they move in the pleasant direction. A home value revised upward after a neighbour sells and never revised down again turns the total into a slowly accumulating optimism.
The defensive habit is to record the date beside the value and treat an estimate older than a year as a guess. Better still, keep a version of the total with the estimated assets excluded. If the two trend differently, the difference is coming from numbers nobody has checked.
Three: what you would owe on the way out
An investment account with a large unrealized gain is worth less than it says, because part of it belongs to a future tax bill. A retirement account holds a balance you cannot reach at face value until a specific age. Neither is a reason to discount them on the balance sheet — the convention of recording assets at market value is the right one, and any after-tax adjustment would need assumptions about a year that has not happened.
It is a reason not to read the total as spendable. Two people with identical net worth, one holding it in a taxable account with a small gain and one holding it in a pre-tax retirement account, are not in the same position.
Four: how concentrated it is
Two portfolios can total the same and carry entirely different exposure. Employer stock plus an employer salary is the version that catches people out, because the two correlate precisely when it matters least — the same event can take both at once.
Concentration is not visible in a total by construction. It shows up only when you group holdings by what they actually depend on, which is rarely how account statements are organized.
What the number is still good for
None of this argues against tracking net worth. It argues against tracking only net worth.
The total is unmatched at one job: showing direction over years, immune to the account-shuffling that makes every other figure look better than it is. Pair it with a liquidity number, an as-of date per estimate, and an occasional look at concentration, and the four blind spots close without giving up the one thing the single number does better than anything else.
This post is educational and general in nature. It is not personalized financial advice.