Savings rate: the number that sets your FIRE date

Two people earn the same salary. One saves a tenth of what lands in the account, the other saves half. The second one does not get there sooner because of better fund picking. They get there sooner because saving half does two jobs at the same time: it fills the pot quicker, and it makes the pot smaller, since the size of the pot is set by what their life costs. That double effect is why the share of income you save, rather than the return you earn, is the number that mostly decides your date.

What a savings rate actually measures

Take what actually arrives in your account over a year, after tax and compulsory deductions. Subtract everything that left. Divide the difference by the income and you have your savings rate. If 3,000 comes in each month and 2,100 goes out, you saved 900, and the rate is 30 percent. The arithmetic is never the hard part. Being honest about what counted as spending is the hard part, and almost everyone's first attempt is too flattering by a wide margin.

Look closely at what the number describes. It is not how much money you put aside. It is the relationship between what you earn and what your life costs to run. Someone saving 900 a month out of 3,000 and someone saving 900 a month out of 9,000 are making identical deposits and are in completely different positions. The first person's life is cheap relative to their income, so their finish line sits much closer. The second person has a lot of money going out of the door, and it is that outgoing figure, not the deposit, that sets the target.

The pot you need is sized off your spending

Financial independence, the idea behind FIRE, just means investments that cover your spending without a salary. Hold onto that definition, because it tells you exactly what the target is made of. The usual way to turn annual spending into a target pot is to divide it by an assumed safe withdrawal rate. Assume you can draw 4 percent a year and the pot works out at 25 times annual spending. Treat that multiple as a planning convention drawn from historical simulations, not as a guarantee, and read the 4 percent rule before leaning on it, because the argument about whether it holds is a real one.

Now watch what one permanent cut does. Suppose you stop paying for something that costs 100 a month, for good. You have 1,200 more a year going into investments. You also need 30,000 less in the pot, because the pot only ever had to cover the spending you actually do. One decision moved the target and the speed of travel in the same direction. No return assumption in the world does that, because a return has no opinion about how much you need.

An illustration you can check on paper

Round numbers on purpose, so the arithmetic stays visible. Someone takes home 40,000 a year and saves 20 percent of it. That is 8,000 saved and 32,000 spent, so at 25 times spending the target is 800,000. Switch investment growth off completely for a second: at 8,000 a year, filling 800,000 takes a hundred years. Same salary, savings rate lifted to 50 percent. Now 20,000 goes in, 20,000 is spent, and the target falls to 500,000. That is 25 years. The rate doubled and the wait dropped to a quarter, because the top and the bottom of the fraction both moved.

Those are illustrative figures with the growth switched off, which is not how investing works. Turn returns back on and both timelines shorten, the hundred-year one enormously, because a very long horizon is precisely where compound interest does its heaviest lifting. The order never flips. And notice what is absent from the whole calculation: the salary. Run the same two cases on 20,000 or on 200,000 and the number of years comes out the same, as long as the rate is the same. That is the reason this one number gets top billing.

A return assumption only pushes on one end

Raise the return you assume and exactly one thing happens: the pot grows faster. The size of the pot you need does not move, because your spending fixed it before any market opened. Raise your savings rate and you get the filling effect and the target effect together. The two levers are not the same shape, even though a spreadsheet lets you type into both with equal confidence.

There is a second difference, and it matters more than the first. Your savings rate is a decision you can verify at the end of the month against your own bank statement. A return is a forecast about markets nobody controls. That leads somewhere uncomfortable: the lower your savings rate, the longer your horizon, and the more of your result is being carried by that forecast. The person saving half their income is asking the market for far less, and is therefore far less exposed to being wrong about it.

How to count yours without fooling yourself

Decide up front how you will treat the three items that muddy every honest attempt. Employer pension contributions are genuine saving, but if they are locked until an age you cannot reach for decades they will not fund an early exit, so count them and keep them in a separate line. Mortgage capital repayment builds equity and behaves like saving, while the interest portion is pure cost, so split the payment rather than counting all of it either way. Paying down a credit card is undoing spending you already did, and treating it as saving makes this year look good at the expense of the years that produced the balance.

Measure over twelve months, never over a good month. Annual insurance, a holiday, a car repair and the dentist do not spread themselves evenly, and a rate computed in a quiet month is fiction. Then cross-check it against net worth, which is where self-deception usually shows up. If your budget says you put away 12,000 last year and your balances moved by nothing remotely like that, one of the two is wrong, and it is normally the budget. Market moves make the comparison rough, so compare contributions where you can rather than raw balances, and run the net worth calculation at the same date each year.

The costs that actually move the number

The items worth attacking are the ones that are large and automatic at the same time. Where you live and how you get around usually dominate a household's outgoings, and each of them is a single decision that then repeats every month with no further effort from you. Skipping a daily coffee is a decision you have to win again tomorrow, and the day after, for a small amount each time. Moving somewhere cheaper, or living without the second car, is decided once and keeps paying while you think about other things.

The other half of the fraction is income, and for many people it is the easier half to move. A raise only lifts your savings rate if the spending stays where it was. If the outgoings quietly rise to meet the new salary, the rate is unchanged, the target has gone up, and the date has not moved at all. That is the entire mechanism behind lifestyle inflation, and it explains how someone can go through a decade of promotions with the same finish line they started with.

Where this arithmetic stops being honest

A high savings rate is not available to everyone, and pretending otherwise is the ugliest habit in this corner of the internet. Below a certain income the essentials take everything, and the answer there is not a stricter budget, it is more income. Even comfortably above that line there is a floor, because the rent has to be paid and someone has to eat, and cutting past a sensible point trades years of the life you are living for years of a projected one. Your health and the people around you are not line items waiting to be optimised. Treat the rate as a dial you set for this season of your life, not as a verdict on how disciplined you are.

Pick a rate you can actually hold

A rate you sustain for ten years beats a rate you hit for two months and then abandon in a heap of resentment. So set it a little below the maximum you think you could bear, and move the money on payday, before the spending gets a chance at it. What is left in the account then becomes the budget, which is a far easier rule to live with than a running tally of restraint. Expect it to change when a job, a child or a move changes the shape of your life.

Here is the thing to do this week. Take last year's income and last year's spending, work your rate out to the nearest five percent, and write it down. Then run the same projection twice, with the return assumption held completely still, changing only the rate by ten points. Watching the finish line move on its own, without a single optimistic assumption about markets, is what makes this number stick.

Written by

Federico Romaldi

Co-Founder, Worthmap

Published: August 14, 2026

Federico is a co-founder of Worthmap, a wealth-intelligence platform built for serious investors. With a background in software engineering and a long-standing passion for value investing, he created Worthmap to bridge the gap between net-worth tracking and investment analysis.