Retire at 40: connect your FIRE target with a saving plan
An age goal becomes useful when it connects to expenses, existing savings and a contribution schedule. Start with the gap you need to fund, then compare timelines.
Define a reproducible scenario
Our examples use a person aged 30, with $4,000 of monthly retirement expenses in today’s US dollars and $100,000 already invested for retirement. Illustrative assumptions are 3% expense inflation, 7% nominal annual return divided by 12 for monthly compounding, a 5% annual contribution increase and a 3.5% withdrawal rate. Contributions arrive at month end.
These amounts illustrate the calculation; they are not estimates of local living costs. Country and currency can be changed in the calculator. The rates are modelling assumptions, not forecasts or recommendations.
Compare retirement at 40, 45 and 50
All values below are in USD, with the assumptions stated above. Open a row to reproduce its inputs. The starting contribution is solved for each target, then increases by 5% annually.
| Retirement age | Monthly expenses then | Target at 3.5% | Required starting investment | Try it |
|---|---|---|---|---|
| 40 | $5,376 | $1,843,085 | $7,757/mo | Open age 40 → |
| 45 | $6,232 | $2,136,641 | $4,325/mo | Open age 45 → |
| 50 | $7,224 | $2,476,953 | $2,691/mo | Open age 50 → |
A longer retirement needs more analysis
Reaching an expense-based target addresses accumulation. It does not prove that money will last through decades of withdrawals. Taxes, fees, healthcare, account access restrictions, pensions, investment losses and retirement duration need separate analysis.
The order of investment returns matters when money is being withdrawn. A constant-return saving projection cannot capture this sequence-of-returns risk.
Review affordability rather than raising the return input
Compare the required starting contribution with what you can reliably invest. A longer timeline, lower expenses or different contribution schedule changes the plan. A larger return input raises the forecast without making that return achievable.
Read the inflation guide, withdrawal-rate comparison and calculation methodology.
Explore a range of retirement outcomes
The worked examples above use fixed returns. The optional Monte Carlo simulation explores varying returns, portfolio withdrawals and percentile outcomes. Try your own assumptions →