Personal finance buries you in numbers (balances, budgets, returns, scores), and most of them flatter you or tell you very little. If you watch just one, make it your savings rate: what percentage of your income stays with you. How to calculate your savings rate fits on one line, and the arithmetic takes about a minute.
Keeping is the part that counts. Two people on the same salary can be decades apart, depending on how much of it each one keeps.
Why the savings rate beats every other number
What you earn is potential. What you keep is what happens. Someone on a high salary who keeps 2% is building almost nothing, because lifestyle creep can swallow any raise.
Someone on an ordinary salary who keeps 25% is building something every month. Earning well and getting somewhere go together far less often than people assume.
It is the one number that sees both sides. Other measures look at what comes in, or at what goes out. The rate puts the two against each other: earn more without spending more and it rises, and spend less on the same income and it rises too. If something you do with your money doesn't move this number, it keeps you busy rather than getting you anywhere.
Raising the rate also helps twice. You put more away each month, and the life you are paying for costs less to run, so the amount you need before work becomes optional shrinks as well.
Here is what that does to the years. Say you start from nothing and earn 5% a year after inflation on what you save. Your target is 25 times your yearly spending, a common goal for financial independence (FI): the point where your savings can pay for your life and work becomes optional.
Saving 10% of your income gets you there in about 50 years of work. Saving 25% takes about 32 years, and saving 50% about 17. Going from 10% to 25% buys back about 20 years.
That is why your savings rate, more than the returns you earn, sets how long this takes.
Your income is how fast money arrives. Your savings rate is whether any of it stays.
How to calculate your savings rate
The formula is one line: (income − expenses) ÷ income, for one month. What makes the number true is what you put into it. Use your take-home income, the money that actually reaches your account, and count all of your spending.
Loan payments are the one tricky case. The part that pays off principal (the money you actually borrowed, as opposed to the interest) adds to your net worth, the value of what you own after your debts. While you are clearing a debt, it is fair to count that part as kept.
What's a good number? Honest answer: better than your last one.
Published benchmarks mislead, because your situation decides so much of it. In a year of low income or high rent, 5% is an achievement, while on a comfortable salary with low rent, 30% may come easily. What matters is which way yours is moving, and that part is in your hands.
Working the rate out by hand every month gets old, which is why Wealth Mutant, our personal finance app, does it from your entries. Reports draws your savings rate as a line, one point for each month, and the multi-year view gives the rate for each whole year. Each entry takes you a few seconds, the app never sees your bank login, and you buy it once.
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Buy — $99 onceCalculated your savings rate? How to raise it
Measure it before you change it
You need real income and real spending, which means writing your spending down. The looking habit comes first here, as it does everywhere else. A rate built on guesses tells you very little.
Start with the spending you won't miss
Begin with the subscriptions you stopped enjoying months ago and the upgrades you got used to so fast you stopped noticing them. Then look at the small automatic purchases, which tend to stop once you start writing them down. None of it is attached to anything you love.
Send part of every raise to savings first
This is the move that changes the number most. Decide now what share of your next raise goes straight to savings (half is a good default), and set it up before the money reaches your spending account. It doesn't hurt, because you never got used to spending it.
Move the kept share on payday
Transfer it the day your pay arrives. Savings that wait for the month's leftovers mostly don't happen.
What changes once you watch it
When the rate is your number, money questions get simpler:
- Should I buy this? Ask what it does to the rate.
- Is this raise good news? Only if some of it reaches the rate.
- Am I doing all right? Check whether the rate is holding or going up.
One number takes the place of a pile of separate worries, and unlike the markets, the economy or your employer, it answers to you.
What you earn impresses people. What you are worth shows up later, as the result. The rate is the cause, and it is the part you can change this month.
To find yours in Wealth Mutant, write down a month of spending, then open Reports and see where your rate sits. The tour walks through everything else built on the same entries.