Project your nest egg from current savings, contributions and expected return.
Future value of an annuity: FV = starter·(1+r)ⁿ + pmt·((1+r)ⁿ−1)/r, with monthly r and n = years×12. Safe withdrawal applies the chosen rate (4 % is the classic Bengen rule) to the final balance.
Retirement planning is the longest-horizon financial decision most people make. The horizon spans decades; the inputs (contribution rate, employer match, expected return, life expectancy, withdrawal rate) compound or amplify each other in ways that intuition handles badly. A small change to the assumed annual return — say, 5 % vs 7 % — can move the projected nest egg by a factor of two over thirty years, which is the difference between an early retirement and working into your seventies. The point of a retirement calculator is not to predict the future precisely (no one can) but to surface the sensitivity of the outcome to each lever. When you can see live that doubling your monthly contribution adds five years of retirement income, the lifestyle trade-off becomes concrete in a way that a spreadsheet rarely makes it.
Two compounding streams. Existing balance grows on its own at monthly rate r = annual_return / 12 over n = years × 12 months: starter × (1 + r)ⁿ. Contribution stream is an ordinary annuity of (your_pmt + employer_match) per month: pmt × ((1 + r)ⁿ − 1) / r. Future value at retirement = sum of both. The employer match in this calc is expressed as a percentage of your contribution (the typical US 401(k) "100 % match up to X %" or French abondement) and is added directly to your monthly pmt before the annuity factor is applied. The safe withdrawal rate at retirement applies a constant percentage (Bengen 1994 found 4 % preserved capital across all 30-year US retirement windows from 1926 onward; modern planners use 3.5–4.5 %) to the final nest egg to give an indicative annual income that should last through retirement under historical sequence-of-returns conditions. For r = 0 the formulas collapse to linear: starter + pmt × n.
Enter your current age and the age you'd like to retire. Add your current savings (the starter balance), your monthly contribution, the employer match as a percentage of your contribution (set to 0 if none), and the expected annual return before fees and inflation. The safe withdrawal rate controls the annual-income KPI — 4 % is the canonical default. The chart redraws the projected balance year by year so you can see the inflection point where compounding overtakes contributions (typically around year 20–25 for a typical earner). Toggle between the three example presets to see how late-starter, mid-career and aggressive-saver paths compare.
Mid-career professional: 35 years old, retiring at 65 (30 years), 30 000 € starter, 500 €/month personal contribution, 50 % employer match (so total monthly = 750 €), 6 % expected annual return, 4 % safe withdrawal.
Nominal vs real returns. The 6 % default is nominal — it doesn't subtract inflation. If you want the result in today's purchasing power (so you can compare to today's expenses), use the real rate: 6 % nominal − 3 % inflation = 3 % real. Otherwise the headline 934 k looks great but represents only ~385 k in 2026 euros at 3 % inflation over 30 years.
Tax wrapper. Returns inside a tax-advantaged account (401(k), Roth IRA, PEA after 5 years in France, ISA in the UK) compound free of capital-gains drag. Outside one, after ~30 % CGT, a 6 % gross return is effectively ~4.2 %. Subtract the CGT as a fee or model the wrapper status explicitly.
Sequence-of-returns risk. The future-value formula assumes a constant rate. Real markets have drawdowns. A 50 % market crash in your final accumulation year can permanently impair the nest egg even if the long-run average return holds. The safe withdrawal rate exists precisely to absorb this — but it doesn't fix the underlying risk.
Employer match limits. Many plans cap the match at a fraction of your contribution (e.g., 100 % of the first 5 % of salary, then 0 %). The calc treats the match as a flat percentage of your contribution; if your plan caps it, set the match percentage so that it matches the cap at your chosen contribution.
4 % rule limitations. The Bengen rule is US-centric, assumes a 60/40 portfolio and 30-year retirement, and was derived from a specific historical window. International equity returns and bond yields have been lower; modern planners often suggest 3.5 % for a 35–40-year retirement to add a safety margin.
Future contributions are not flat. Most savers escalate contributions over time as salary rises. The calc uses a constant monthly contribution; reality is closer to step-ups. To approximate, use a higher average contribution that reflects your expected career trajectory.