Calculation details
Planning estimate only, not financial, tax, or legal advice. Verify assumptions and current rules before making decisions.
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Use this result
Share the current inputs or ask ChatGPT to explain the calculation in context.
What does this calculator estimate?
Saving $1,000 per month for 30 years at a 7 percent annual return compounds to about $1.22 million before inflation. The calculation grows the balance monthly at return / 12 and adds each contribution at the chosen timing.
- Monthly compounding applies annual return divided by 12 to each month's balance (Investor.gov).
- Inflation-adjusted real value discounts the nominal total by the assumed inflation rate.
- Starting ten years earlier roughly doubles the end balance at the same contribution rate.
How retirement projections work
Retirement planning compounds current savings and monthly contributions to a future balance, then estimates how much income that balance supports. The 4% rule — withdrawing 4% annually, adjusted for inflation — is the common sustainable-withdrawal benchmark.
Limitations to watch for
The projection is a scenario, not a promise: returns vary, and sequence-of-returns risk matters near retirement. The 4% rule is a historical guideline, not a guarantee. Taxes, inflation, and Social Security/pensions are separate inputs.
How to use it in practice
Enter your current balance, monthly contribution, assumed return (7% nominal is a common long-term assumption), and years to retirement. Compare the projected income against your expected needs. Increase contributions or extend the horizon if the gap is large.
['Enter current savings and monthly contributions.', 'Enter the assumed return and years to retirement.', 'Read the projected balance and sustainable annual income.']
How retirement planning works
The calculator projects the balance from current savings and monthly contributions at an assumed return, then estimates the income it can produce. It links the accumulation phase to the withdrawal phase so the goal has a number.
The 4 percent rule
A common withdrawal screen: 4 percent of the portfolio in year one, adjusted for inflation. A $1 million portfolio supports about $40,000 of first-year income. The calculator applies the rule to the projected balance.
Real vs. nominal returns
Planning should use real returns (nominal minus inflation): 7 percent nominal with 3 percent inflation is 4 percent real. The calculator's real-return input keeps the projected income honest about purchasing power.
A worked example
$100,000 saved, $1,000 monthly, 5 percent real return, 25 years: the portfolio reaches about $680,000, supporting roughly $27,200 per year at 4 percent. The calculator returns the balance and the income.
The variables that decide
Return assumptions, contribution rate, retirement age, and withdrawal rate dominate the projection. The calculator's scenario inputs let you test the plan's sensitivity before the market does it for you.
How this calculator works
Formula
Projects future value of current savings + monthly contributions at an assumed return, then estimates the sustainable annual withdrawal (often 4% of the balance) in retirement.
Worked example
$500/month for 30 years at 7% grows to about $610,000 — supporting roughly $24,400/year at a 4% withdrawal rate.
Assumptions to verify
- A constant return over the full horizon.
- Withdrawals follow the 4% rule.
- No taxes or inflation adjustments are modeled.
Frequently asked questions
How much do I need for retirement?
Project your balance, then apply the 4% rule: $610,000 supports about $24,400/year.
What is the 4% rule?
Withdrawing 4% of the balance in year one, adjusted for inflation — historically sustainable over 30-year retirements.
What return should I assume?
7% nominal is a common long-term assumption for diversified portfolios; use less for conservative planning.
Does this include Social Security?
No — add expected Social Security/pension income separately to the projected withdrawals.
Why is my number so uncertain?
Returns, inflation, and sequence risk all vary — the projection is a scenario. Stress-test with lower returns.
When should I start?
Now — every year of compounding reduces the monthly contribution needed.
What's the rule of 25?
Multiply your desired annual retirement income by 25 for the approximate balance needed (the inverse of 4%).
How much do I need to retire?
Roughly 25× your desired annual income — the 4% rule's reverse.
How much should I contribute?
The calculator shows the monthly contribution needed for a target balance.
Cite this tool
BoringToolsKit. “Retirement Planning Calculator.” boringtoolskit.com/retirement-planning-calculator/ (reviewed 2026-08-25). Free to reference in articles, syllabi, and answer posts with a link.
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