Understanding retirement planning
Retirement planning comes down to one question: will the money you save, plus its growth, be enough to support you once you stop working? This calculator projects how your current savings and ongoing contributions could grow by your target retirement age, and how long that nest egg might last. It turns a vague worry into concrete numbers you can act on.
The three forces at work are how much you contribute, the return your investments earn, and — most powerfully — the number of years your money has to compound. Because of compounding, the contributions you make in your twenties and thirties do far more heavy lifting than those made later.
How the projection works
The calculator grows your current balance and each future contribution at your assumed annual return until your retirement age, using compound growth. It then estimates how long the resulting balance can support your desired annual withdrawals, accounting for continued growth on the money still invested.
Future value = current savings compounded + all contributions compounded
A worked example
A 30-year-old with $25,000 saved, contributing $600 a month, earning a 7% return, retiring at 65:
| At retirement (age 65) | Value |
| Projected balance | $1.29M |
| Total contributed | $277,000 |
| Investment growth | ~$1.01M |
Roughly 78% of the final balance is growth, not contributions. Delaying the start by just 10 years — beginning at 40 instead of 30 with the same $600/month — would cut the balance to around $610,000, less than half, despite contributing only $72,000 less.
The 4% rule: A widely cited guideline suggests you can withdraw about 4% of your retirement balance in the first year, then adjust for inflation, with a reasonable chance the money lasts 30 years. Under this rule, a $1.29M balance supports roughly $51,600 of first-year withdrawals. It is a starting point, not a guarantee — market conditions and lifespan vary.
Key retirement accounts
401(k)
Employer-sponsored, often with a matching contribution. Always contribute at least enough to capture the full match — it is an immediate, guaranteed return on your money.
Traditional vs Roth
Traditional accounts give you a tax break now and are taxed on withdrawal; Roth accounts are funded with after-tax money and grow tax-free. Roth is often favored when you expect to be in a higher tax bracket later.
IRAs
Individual Retirement Accounts supplement workplace plans and offer more investment choice. They come in traditional and Roth versions with their own contribution limits.
Common mistakes to avoid
- Starting late. The single biggest and most irreversible mistake — lost compounding years cannot be recovered.
- Leaving the employer match on the table. Not contributing enough to get the full match is declining free money.
- Cashing out on a job change. Rolling over preserves compounding; cashing out triggers taxes, penalties, and lost growth.
- Ignoring inflation. A dollar decades from now buys less; plan in real terms.
- Being too conservative too early. Overly cautious investing in your twenties can leave large sums on the table.
Frequently asked questions
How much do I need to retire?
A common approach is estimating your desired annual spending and multiplying by about 25 (the inverse of the 4% rule). The right number depends on your lifestyle, other income sources, and life expectancy.
What is the 4% rule?
It suggests withdrawing about 4% of your balance in your first retirement year, then adjusting for inflation, with a reasonable chance of lasting 30 years. It is a guideline, not a guarantee.
Should I choose a traditional or Roth account?
Traditional accounts give a tax break now and are taxed later; Roth accounts are taxed now and grow tax-free. Roth often wins if you expect higher taxes in retirement.
Why does starting early matter so much?
Compounding produces its largest gains in the final years, so early contributions have more time to multiply. Delaying even a decade can roughly halve your final balance.
How much should I contribute?
At minimum, enough to capture your full employer match. Many planners suggest saving 15% of gross income for retirement, including any match.
Sources & references
- U.S. Department of Labor — retirement plans and 401(k) basics · dol.gov
- U.S. Securities and Exchange Commission — retirement investing · investor.gov
Estimates are for educational purposes only and are not financial advice. Returns are not guaranteed and inflation will affect real outcomes.