In Short
Your FI number is the yearly spending your investments must cover, divided by a withdrawal rate. Spending $60,000 a year at the 4% rule of thumb means $1.5 million; $20,000 a year of Social Security or other income cuts it to $1 million. The 4% rule comes from historical studies, not a guarantee, and your own benefit estimate is in your my Social Security account [1].
How to Use the Financial Independence Calculator
- Enter what you'd spend a year once work is optional, in today's dollars.
- Set a withdrawal rate (4% is a rule of thumb) and add any Social Security, pension or rental income.
- Enter what you've invested, what you save a year and a return after inflation.
- Or tap Say It All: “I'm 40, I spend 80,000 a year, I have 400,000 invested, I save 40,000 a year, Social Security will pay 24,000.”
The Formula
The FI number is the portfolio that could pay your spending gap at your withdrawal rate. The calculator then grows your investments month by month at a real (after-inflation) return until they reach it, so every number stays in today's dollars [3].
- FI number = (yearly spending − other income) ÷ withdrawal rate
- At 4%: FI number = spending gap × 25
- Each month: balance × (1 + real return)^(1/12) + yearly savings ÷ 12
- Savings rate = yearly savings ÷ take-home pay
Worked Examples
| Scenario | Inputs | Result |
|---|---|---|
| Classic 4% rule | Age 35, $60,000/year spending, $150,000 invested, $30,000/year saved, 5% real | FI number $1,500,000 · 20.9 years · age 55 · 30% savings rate |
| With Social Security | Same, plus $20,000/year of Social Security | FI number $1,000,000 · 15.4 years · age 50 |
| Business owner at 40 | $80,000 spending, $24,000 other income, $400,000 invested, $40,000/year, 5% real | FI number $1,400,000 · 12.3 years · age 52 |
| More cautious 3.5% rate | Age 30, $40,000 spending, $50,000 invested, $25,000/year, 5% real | FI number $1,142,857 · 22.2 years · age 52 |
Illustrative examples, not projections. Figures use the tax year shown and the assumptions above.
What Is the 4% Rule?
It's a rule of thumb from historical studies of U.S. stock and bond returns: a retiree who took 4% of the portfolio in year one, then the same dollar amount adjusted for inflation each year, would have lasted at least 30 years in nearly all of the historical periods studied. It is not a guarantee. The future can differ from the past, and retirements longer than 30 years may call for a lower rate.
Sequence-of-returns risk is part of why. Two retirees with the same average return can end up very differently if one meets a market drop in the first years of withdrawals: selling while prices are down leaves less to recover.
How Does Social Security Change My FI Number?
Every dollar of steady income you'll have in retirement is a dollar the portfolio doesn't have to pay. At 4%, $20,000 a year of Social Security lowers the FI number by $500,000. Your personal benefit estimate is in your my Social Security account at ssa.gov [1].
Benefits can start at 62 at the earliest, with a permanent reduction for claiming before full retirement age [2]. If you reach FI earlier, the portfolio has to cover all your spending until benefits begin.
Why Does the Savings Rate Matter So Much?
Saving more does two things at once: it adds to the portfolio and it shows you can live on less, which lowers the FI number. A household that saves 30% of take-home pay needs far fewer years than one that saves 10%, whatever its income.
Frequently Asked Questions
How much do I need to retire early on $60,000 a year?
At the 4% rule of thumb, $1.5 million (25 × $60,000). At a more cautious 3.5%, about $1.71 million. Social Security or other income lowers it.
Is the 4% rule safe?
It's a rule of thumb from historical U.S. returns, not a guarantee. Poor returns early in retirement (sequence-of-returns risk), high fees or a very long retirement can make it too high.
What return should I use for financial independence?
This calculator uses a real return, after inflation, so results are in today's dollars. Many people test a range, such as 4% to 6%, rather than rely on one number.
Where do I find my Social Security estimate?
Sign in to your my Social Security account at ssa.gov to see your estimated benefits at different claiming ages [1].
Does the FI number include taxes?
Only if you include them in your spending. Withdrawals from traditional 401(k)s and IRAs are taxable, so many people add an estimate of tax to the yearly spending figure.
Sources
- my Social Security account — Social Security Administration
- Retirement Benefits: Starting Your Retirement Benefits Early — Social Security Administration
- Consumer Price Index (CPI) — U.S. Bureau of Labor Statistics
Official sources only: the IRS, SSA, BLS and other government agencies. Read how Zentavos researches.