Retirement Calculator

This retirement calculator estimates the whole savings gap, not one account’s tax treatment. It asks how much you have saved, how much you add each month, what return you expect before retirement, what return you expect during retirement, how much monthly income you want in today’s dollars, how long retirement should last, and what inflation rate to apply. It then compares projected savings with the estimated nest egg needed to support that income stream.

This is informational, not financial advice. Retirement rules, tax laws, account contribution limits, Social Security claiming rules, pension formulas, health costs, and market conditions change. The calculator is a deterministic planning model that matches its calculation; it does not guarantee retirement readiness or replace a fiduciary financial plan.

What this calculator measures

The calculator has two sides. The accumulation side grows your current savings and monthly contributions from now until retirement. The spending side inflates your desired monthly income to the first year of retirement and calculates the present value, at retirement, of that monthly income for the number of retirement years entered. The difference is the surplus or shortfall.

That makes this page broader than the 401(k) calculator, which focuses on workplace salary deferrals and employer match, and broader than the IRA calculator, which focuses on pre-tax individual account tax treatment. It is also distinct from the pension calculator and social security retirement calculator, which estimate income sources that can reduce the amount you need from savings. If you are deciding whether to work longer, the retirement age calculator can complement the result.

Formula used by the calculator

First, the calculator grows current savings and monthly contributions until retirement:

$\text{projected nest egg} = \text{current savings}(1 + \text{pre retirement monthly return})^{\text{months to retirement}} + \text{monthly contribution} \times \frac{(1 + \text{pre retirement monthly return})^{\text{months to retirement}} - 1}{\text{pre retirement monthly return}}$

Next, it inflates today’s income goal to the first retirement year:

$\text{first retirement monthly income} = \text{desired monthly income today} \times (1 + \text{inflation rate})^{\text{years to retirement}}$

Then it calculates the nest egg needed to fund that monthly payment during retirement:

$\text{needed nest egg} = \text{first retirement monthly income} \times \frac{1 - (1 + \text{retirement monthly return})^{-\text{retirement months}}}{\text{retirement monthly return}}$

The gap is:

$\text{gap} = \text{projected nest egg} - \text{needed nest egg}$

If the gap is negative, the result is a projected shortfall. If it is positive, the result is a projected surplus.

Worked example

With the default inputs, the person is age 35 and plans to retire at 65. Current retirement savings are $50,000. Monthly contributions are $800. The expected return before retirement is 7 percent, the return during retirement is 4 percent, desired monthly income is $4,500 in today’s dollars, retirement lasts 25 years, and inflation is 2.5 percent.

There are 30 years to retirement, or 360 monthly contribution periods. The current $50,000 and $800 monthly deposits grow at a monthly rate of 7 percent divided by 12. The projected nest egg is $1,381,801.67. The $4,500 monthly income goal is then inflated for 30 years at 2.5 percent, producing a first-year monthly retirement income target of $9,439.05.

The calculator treats that $9,439.05 monthly income as a 25-year withdrawal stream, or 300 months, discounted at a monthly retirement return of 4 percent divided by 12. The estimated nest egg needed is $1,788,252.24. The projected nest egg is lower than the needed amount by $406,450.57, so the primary result is a projected shortfall. Under the same assumptions, the required monthly saving is $1,133.16, which is $333.16 more than the current $800 monthly contribution.

What the result does not include

The model does not tax retirement withdrawals. A $1 million traditional 401(k) balance and a $1 million Roth balance can have different spending values. It also does not model Social Security, pensions, annuities, home equity, inheritance, health insurance premiums, long-term care, debt payoff, or one-time purchases. You can incorporate outside income by lowering the desired monthly income that must come from savings, but you should document the assumption.

The withdrawal side is a present-value estimate, not a safe withdrawal rule. It assumes a steady monthly income, a steady retirement return, and a fixed number of retirement months. Real retirement spending often changes over time, investment returns arrive unevenly, inflation can spike, and longevity is uncertain.

Practical tips

• Run a conservative return and a higher inflation scenario to see how fragile the plan is.
• Test retiring later; extra working years both add contributions and shorten the withdrawal period.
• Reduce the desired monthly income only after estimating Social Security, pensions, or other reliable income sources.
• Revisit the calculation yearly because savings, income goals, and market balances change.
• Treat the required monthly saving as a planning target, not a promise that one number solves retirement.

Sources

• U.S. Department of Labor, Types of retirement plans — overview of retirement plan structures.
• IRS, Required minimum distributions FAQs — retirement account distribution context.

Formula references

• Claim: compound current savings and end-of-month contributions to retirement; inflate desired income; value retirement withdrawals as an ordinary annuity at post-retirement monthly return. Source: Compound Interest Calculator, U.S. Securities and Exchange Commission, Investor.gov. Version: live federal investor tool accessed 2026-07-09. Jurisdiction: United States; arithmetic is general. Accessed 2026-07-09.
• Claim: compound current savings and end-of-month contributions to retirement; inflate desired income; value retirement withdrawals as an ordinary annuity at post-retirement monthly return. Source: Principles of Finance, OpenStax, Rice University (peer-reviewed open textbook). Version: 2022 first edition, ISBN 978-1-951693-54-1. Jurisdiction: Jurisdiction-neutral finance definitions. Accessed 2026-07-09.

These sources support only the claims described above. This calculator is informational and does not replace qualified domain, legal, consumer-credit, payroll, mortgage, pensions, or retirement advice.