Retirement Calculator

Retirement planning is a math + behavior problem

A retirement plan typically answers two questions: how much you might have by a certain age, and whether that amount can support your desired spending. This calculator estimates both using a simple compounding model and a withdrawal-rate planning assumption.

The projection uses your current savings, monthly contribution, and an average annual return. The target uses your desired annual spending in today’s dollars, inflates it to your retirement year, and then estimates a required “nest egg” using a withdrawal rate (often discussed as the 4% rule).

These are planning assumptions, not guarantees. The value comes from comparing scenarios: contributing more, retiring later, adjusting spending expectations, or using a more conservative return assumption.

Projected balance: what it represents

The projected balance is the estimated size of your retirement portfolio at retirement age, given your current savings, monthly contributions, and an average annual return assumption. The model is intentionally simple: contributions are added monthly and growth is applied monthly.

Because returns are not smooth in real life, the projection should be interpreted as a long-run expectation, not a promise. If you want to plan conservatively, you can lower the return input or increase the inflation input to reduce the “real” purchasing power of the projection.

Required balance: linking spending to savings

To estimate a target balance, the calculator inflates your desired annual spending from today into retirement-year dollars. Then it divides that spending by a withdrawal rate (for example 4%). The result is an estimate of the portfolio size needed to support that spending level.

Withdrawal rate is a planning knob. A lower withdrawal rate implies a larger required balance but can be more conservative. Your personal situation—retirement horizon, risk tolerance, other income sources—can justify using a lower or higher rate.

Closing the gap: what usually works best

If your projected balance is below the required balance, the “gap” is your shortfall. The most reliable levers to close the gap are increasing contributions and extending time (retiring later). Higher return assumptions can help on paper, but they also increase uncertainty.

A useful approach is to set a realistic contribution you can maintain, then adjust retirement age or spending target until the gap is near zero. You can then revisit the plan annually as income, savings, and market conditions evolve.

Limitations and what to personalize

This calculator is intentionally simple: it does not model taxes, Social Security, pensions, healthcare premiums, required minimum distributions, or changing contribution rates over time. Those factors can materially change real retirement outcomes.

If you want a more personalized plan, treat this tool as your “core engine” and then adjust the spending target downward to reflect other income sources, or adjust the return assumption to reflect your expected portfolio mix.

A strong habit is to re-run your plan once per year. Small course corrections—raising contributions, updating spending goals, or adjusting retirement age—can be easier than large changes later.