Retirement Savings Goal Calculator: How Much Do You Need to Retire?
Estimate the total nest egg you need to retire comfortably using the 4% safe withdrawal rule, inflation adjustments, and your expected Social Security or pension income.
Formulas Used
1. Inflation-Adjusted Future Expenses:
Future Annual Expenses = Annual Expenses × (1 + inflation rate)years to retirement
2. Net Annual Portfolio Withdrawal:
Net Need = Future Annual Expenses − Future Social Security / Pension
3. Total Nest Egg Required (Present Value of Retirement Annuity):
Nest Egg = Net Annual Need × [1 − (1 + rreal)−n] / rreal
where rreal = (1 + nominal return) / (1 + inflation) − 1 and n = years in retirement
4. Future Value of Current Savings:
FVsavings = Current Savings × (1 + annual return)years to retirement
5. Future Value of Monthly Contributions:
FVcontrib = Monthly Contribution × [((1 + rmonthly)12 × years − 1) / rmonthly]
where rmonthly = annual return / 12
6. Savings Gap:
Gap = Nest Egg Required − (FVsavings + FVcontrib)
7. Additional Monthly Savings to Close Gap:
Additional Monthly = Gap × rmonthly / [(1 + rmonthly)n months − 1]
Assumptions & References
- The 4% Safe Withdrawal Rule (Bengen, 1994; Trinity Study) suggests withdrawing 4% of your portfolio annually in retirement is sustainable for 30 years. This calculator uses a more precise annuity-based approach.
- Inflation is applied to both expenses and Social Security / pension income to express all values in retirement-day dollars.
- The real rate of return adjusts the nominal investment return for inflation, providing a conservative and accurate annuity calculation.
- Social Security benefits are assumed to begin at retirement age and are inflation-adjusted from today's estimate.
- Monthly contributions are assumed to be made at the end of each month (ordinary annuity).
- Investment returns are assumed to be consistent and compounded annually (monthly for contributions).
- This calculator does not account for taxes, healthcare costs, or sequence-of-returns risk.
- References: Bengen (1994) Journal of Financial Planning; Cooley, Hubbard & Walz (1998) Trinity Study; Fidelity Retirement Guidelines; Vanguard Retirement Research.