Retirement Savings Projector: Contributions, Growth and Purchasing Power

Use this calculator to explore how an existing balance and regular monthly deposits might grow before retirement. It shows both future dollars and their purchasing power under your inflation assumption. A separate withdrawal percentage translates the ending balance into an illustrative first-year withdrawal, before tax.

The calculator uses constant growth, fixed monthly deposits, and a separate inflation assumption. It projects accumulation and an initial withdrawal amount; evaluating how long withdrawals last requires a retirement spending model. Use the examples below to compare contribution and return scenarios.

Choose inputs that describe the same plan

Enter the savings you intend to use for retirement, excluding an emergency fund or money earmarked for a nearer purchase. The monthly contribution stays constant in nominal dollars until the retirement age entered. Include employer contributions only to the extent they belong in the scenario you are modeling; the tool does not automatically add a match or apply a vesting schedule.

The return input is an effective annual return after assumed investment fees, before taxes and inflation. For example, entering 7 means that a balance with no deposits grows exactly 7% over one modeled year. It does not mean 7% divided by twelve and compounded monthly, which would produce a higher effective annual rate.

Enter inflation separately. A 3% inflation assumption reduces the purchasing power shown; it does not reduce the nominal account balance. Keep a copy of your assumptions so that a later change in results can be traced to a new balance, contribution or return rather than confused with actual investment performance.

How the monthly calculation works

The equivalent monthly growth rate is:

Monthly rate = (1 + effective annual return)^(1/12) − 1

At each month-end, the calculator applies growth to the existing balance and then adds the contribution. It repeats that process twelve times for each year until retirement. At 7% effective annual growth, the monthly rate is approximately 0.5654%.

The table combines starting savings and subsequent deposits in one contribution total. Modeled growth is the change generated during this projection, and becomes negative when the assumed return is negative. The starting balance’s earlier contribution and growth history remains outside the calculation.

Today-dollar value equals the future balance divided by (1 + inflation)^years. Both investment growth and inflation are constant in the model. The SEC’s compound-interest calculator offers another way to explore accumulation assumptions; confirm its rate and compounding conventions before comparing outputs.

Worked example: age 30 to age 65

Assume a 30-year-old starts with $50,000, deposits $500 at each month-end for 35 years, earns a constant effective annual 7% after fees and experiences 3% annual inflation. With a 4% initial withdrawal illustration, the results are:

Output	Calculated amount
Initial savings plus new deposits	$260,000.00
Final balance in future dollars	$1,389,535.89
Modeled growth during the projection	$1,129,535.89
Final balance in today’s purchasing power	$493,817.99
Illustrative monthly withdrawal, future dollars	$4,631.79
Same monthly withdrawal in today’s purchasing power	$1,646.06

For a budget written in today’s dollars, use the $1,646.06 inflation-adjusted monthly withdrawal. Then include taxes and other income. Pretax and Roth accounts can deliver different after-tax spending amounts; see Traditional IRA versus Roth IRA when assigning withdrawals to account types.

Run sensitivity cases before deciding you are on track

Keeping the default $50,000 balance, $500 monthly deposit and 35-year horizon produces these future-dollar balances:

Effective annual return after fees	Hypothetical ending balance
3%	$508,427.11
5%	$830,032.26
7%	$1,389,535.89
9%	$2,367,520.72

The range shows how strongly the assumed return affects the outcome. Compare the 3%, 5%, and 7% rows with the saving target before relying on the higher-return case. Test a larger contribution or a later retirement date to see which adjustment closes the gap under lower returns.

Under the 7% scenario, adding $50 a month increases the ending balance by about $85,570.68 over 35 years. Repeat that deposit change at the lower return assumptions. This compares a contribution decision you can make with market outcomes that remain uncertain.

Understand what the withdrawal percentage means

William Bengen’s October 1994 research examined historical retirement withdrawals and asset allocations. The familiar 4% approach starts with a percentage of the initial retirement balance, then adjusts the dollar withdrawal for inflation in later years. Original research, reprinted by the Financial Planning Association.

This calculator performs only the first multiplication. A $1 million balance at 4% gives $40,000 for the first year, or $3,333.33 per month before tax. Under an inflation-adjusted spending approach and an assumed 3% inflation rate, the next year’s withdrawal would be $41,200. Taking 4% of whatever balance remains each year is a different strategy.

Try 3%, 3.5%, and 4% to compare initial withdrawal amounts. Then evaluate the chosen schedule over retirement, including longevity, spending changes, and early market losses. Use that longer analysis to set withdrawals and review rules.

Check contribution limits separately

The deposit field accepts a total across accounts and does not enforce tax-law eligibility. For 2026, the standard employee 401(k) deferral limit is $24,500 and the IRA contribution limit is $7,500. IRA catch-up contributions add $1,100 at age 50 or older; workplace catch-up provisions have different amounts and age rules. Income, compensation and plan requirements can further affect eligibility. IRS 2026 retirement limits

A $3,000 monthly deposit equals $36,000 annually. Assign that amount to eligible accounts—workplace contributions, IRAs, or other savings—and check each limit. Include the employer match explicitly if it is part of the assumed contribution.

Use the 401(k) versus IRA guide to distinguish account roles, and the fee impact tool to estimate how a chosen cost assumption affects accumulation. Do not subtract a fee again when the return entered here already accounts for it.

Add benefits, taxes and a spending budget

Social Security and pensions are excluded. Obtain your own benefit estimates by claiming age through my Social Security, rather than inserting a national average. Confirm whether any benefit estimate is expressed in current or future dollars before combining it with this output.

For a budget in today’s dollars, $4,000 monthly spending minus $2,200 dependable benefits leaves a $1,800 gap, or $21,600 annually. At an initial 4%, that corresponds to $540,000; at 3.5%, about $617,143. Add any omitted taxes, then test the withdrawal schedule across the retirement horizon.

Also list one-time expenses, healthcare costs and debt payments that change over time. A single constant monthly budget can hide an expensive early retirement period or a later reduction after a mortgage ends.

Revisit the projection when the plan changes

Rerun the projection after changes in savings, retirement age, contributions, or investment costs. Save the previous inputs so you can identify which change produced the new result and update the contribution plan accordingly.

For a zero-year horizon, the result is today’s balance and no additional deposits. With zero starting savings and zero contributions, all dollar results remain zero. If a result depends on uninterrupted deposits for decades, add a second scenario with a smaller deposit to see how employment interruptions could affect the plan. The purpose is to expose assumptions that deserve attention before making retirement commitments.

Sources

Reviewed November 3, 2026: SEC compound-interest calculator, Bengen’s 1994 research, IRS 2026 contribution limits, and SSA benefit estimates. Worked examples use the inputs and timing described above.