Retirement Savings Growth Calculator

Retirement savings growth calculator for projecting your future balance

This retirement savings growth calculator estimates how much your retirement fund could be worth by the time you reach your target retirement age. It uses your current balance, monthly contributions, and an expected annual return rate to model compounding over time. You can also include fees, inflation, and contribution increases to get a more realistic view of what your savings might feel like in today’s money.

The main result is your projected retirement balance at retirement age. Alongside that, the calculator shows how much of that total comes from your own contributions versus investment growth. This matters because two people can end up with the same final balance for very different reasons, and that changes how stable the plan is. A plan built mostly on contributions is less sensitive to market returns, while a plan built mostly on growth is more sensitive to return assumptions.

For practical planning, the calculator also estimates a simple retirement income guideline using the commonly referenced “4% rule.” This is not a guarantee. It is a rough planning tool that estimates a sustainable annual withdrawal amount from a diversified portfolio under certain historical assumptions. It is included because most people need to translate a single big number into a monthly income figure to sanity-check whether the projection is useful.

Assumptions and how to use this calculator

• Returns are modeled as a smooth monthly compound rate derived from your annual return assumption. Real markets fluctuate and can produce very different outcomes.
• Fees, if included, reduce your assumed annual return. This is a simplification that approximates the long-term impact of ongoing fund fees.
• Inflation, if included, is used to estimate a “today’s money” value by discounting the final balance. Inflation can vary and does not move in a straight line.
• Contribution increases, if included, raise your monthly contribution gradually over time. If you do not know this value, leaving it blank still produces a valid projection.
• This calculator does not include taxes, withdrawals before retirement, employer matching rules, or guaranteed income products. Treat it as a planning estimate, not a financial statement.

Common questions

Why does a small change in return rate make such a big difference?

Compounding multiplies over time. When you project 20 to 40 years into the future, a 1% difference in annual return changes the growth rate applied to every month. That effect stacks, so the gap can become large. If you want a more conservative estimate, reduce your return assumption and include a fee value.

What should I enter for fees if I am unsure?

If you do not know your all-in fund fees, leaving the fee field blank is acceptable. If you want a reality check, try a fee of 0.5% to 1.5% and compare results. Fees are a long-term drag because they compound negatively over the same time horizon as your investment growth.

What does “inflation-adjusted balance” mean?

The inflation-adjusted balance is a rough estimate of what your projected retirement balance would be worth in today’s spending power. For example, if inflation averages 5% per year, a future amount might look large but buy less than you expect. This calculator discounts the final balance to show a “today’s money” comparison.

Do I have to fill in optional fields to get a result?

No. Fees, inflation, and contribution increases are optional. If you skip them, the calculator uses reasonable defaults (0% fees, 0% inflation, 0% contribution increases) and still produces a useful projection. Add optional inputs only when you want a more realistic model.

Is the 4% rule safe to rely on for retirement planning?

It is a guideline, not a promise. It is based on historical market performance in specific regions and time periods, and real outcomes depend on your asset mix, taxes, fees, retirement length, and market conditions early in retirement. Use it as a quick way to convert a portfolio value into an estimated annual and monthly income target, then validate with more detailed planning.