See the balance, the split between contributions and growth, and what it actually buys.
Final balance
$529,820
After 0.15% in fees, before inflation.
At 3% inflation.
After fees, before inflation.
Contributing $600 a month for 25 years on top of $10,000 means you put in $190,000. The remaining $339,820 is compound growth, which is 64% of the final balance. Growth overtakes contributions in year 18, which is why the early years feel slow and the later ones do not.
At 3% inflation over 25 years, prices roughly double — so the purchasing power of your final balance is closer to $253,045 in current terms. This is the single most important adjustment in long-range planning, and the one most calculators omit. Plan against the inflation-adjusted figure.
Raising your contribution from $600 to $700 adds $79,110 to the final balance — you contribute $30,000 more and compounding supplies the rest. Contribution rate is the dominant variable in the first decade; returns take over later.
At year 15 you would have $215,576. The final decade adds $314,244 — more than 59% of the ending balance, from only $72,000 of additional contributions. This is why staying invested through the unremarkable middle years matters more than any single decision about what to buy.
A balance is only meaningful against a target. If this is retirement money, the retirement calculator converts it into a sustainable annual income and tells you whether $529,820 is enough. If it is a specific purchase, the savings goal calculator works backwards from the number you need.
Turn this into retirement incomeWorked scenarios with the full analysis, so you can see how the numbers move before entering your own.
A steady mid-career investor, showing the point where compound growth overtakes contributions.
Final balance
$529,820
Contributing $600 a month for 25 years on top of $10,000 means you put in $190,000. The remaining $339,820 is compound growth, which is 64% of the final balance. Growth overtakes contributions in year 18, which is why the early years feel slow and the later ones do not.
At 3% inflation over 25 years, prices roughly double — so the purchasing power of your final balance is closer to $253,045 in current terms. This is the single most important adjustment in long-range planning, and the one most calculators omit. Plan against the inflation-adjusted figure.
Raising your contribution from $600 to $700 adds $79,110 to the final balance — you contribute $30,000 more and compounding supplies the rest. Contribution rate is the dominant variable in the first decade; returns take over later.
A 40-year horizon showing what an extra decade of compounding is worth on identical contributions.
Final balance
$1,374,076
Contributing $500 a month for 40 years on top of $5,000 means you put in $245,000. The remaining $1,129,076 is compound growth, which is 82% of the final balance. Growth overtakes contributions in year 18, which is why the early years feel slow and the later ones do not.
At 3% inflation over 40 years, prices roughly double — so the purchasing power of your final balance is closer to $421,232 in current terms. This is the single most important adjustment in long-range planning, and the one most calculators omit. Plan against the inflation-adjusted figure.
Raising your contribution from $500 to $600 adds $258,825 to the final balance — you contribute $48,000 more and compounding supplies the rest. Contribution rate is the dominant variable in the first decade; returns take over later.
The same portfolio carrying a typical advisory fee, showing the compounding drag over 30 years.
Final balance
$1,606,773
Contributing $1,000 a month for 30 years on top of $100,000 means you put in $460,000. The remaining $1,146,773 is compound growth, which is 71% of the final balance. Growth overtakes contributions in year 17, which is why the early years feel slow and the later ones do not.
At 3% inflation over 30 years, prices roughly double — so the purchasing power of your final balance is closer to $661,969 in current terms. This is the single most important adjustment in long-range planning, and the one most calculators omit. Plan against the inflation-adjusted figure.
Fees compound against you exactly as returns compound for you. Moving from 1% to a typical index fund's 0.05% would leave you with $2,007,638 instead of $1,606,773 — a difference of $400,866. It is also the only variable in this entire calculation you can change with certainty.
Compound interest is return earned on previous returns. In year one you earn a return on your contributions. In year two you earn a return on your contributions plus year one's return. The base grows every period, which is why the curve bends upward rather than running straight.
The practical consequence is that outcomes are extremely sensitive to time and only moderately sensitive to rate. Someone contributing $500 a month from age 25 to 65 at 7% ends with substantially more than someone contributing $1,000 a month from 40 to 65, despite the second person contributing more in total. The first person's early dollars had forty years to compound.
A 1% annual fee sounds small against a 7% return — roughly a seventh of the gain. Over thirty years it is closer to a quarter of the final balance, because each year's fee also removes the compounding that money would have produced for every remaining year.
This is why the shift to low-cost index funds has been the single largest improvement in retail investor outcomes over the past two decades. Broad-market index funds now commonly charge 0.03–0.10%, against 0.5–1.5% for actively managed alternatives and often another 1% for advisory services layered on top.
A projection showing $2.1 million in thirty years is describing dollars that will buy considerably less than dollars today. At 3% inflation, thirty years reduces purchasing power to roughly 41% of current value, so that $2.1 million buys about what $865,000 buys now.
Two approaches work. Project in nominal terms and then deflate the final figure, which is what this calculator does. Or use a real return assumption — roughly 4% instead of 7% — from the start, which produces a final number already expressed in today's dollars. What does not work is projecting nominally and then comparing the result against today's expenses.
A $2 million projection ignores that thirty years of inflation cuts purchasing power by more than half. Always check the real value.
Planning at 10% rather than 7% produces a plan that under-saves for decades, with the error only becoming visible when it is too late to fix.
The difference between 0.05% and 1% is roughly a third of the final balance over thirty years, and it is entirely within your control.
Contributions made during declines buy more shares. Stopping them removes the mechanism that makes recoveries profitable.
Growth in a 401(k) or Roth is untaxed along the way. Applying a tax drag to those accounts understates the outcome.
Seven percent nominal is a common planning figure for an equity-heavy portfolio, reflecting roughly 10% long-run US market returns minus about 3% inflation. Balanced portfolios with significant bond allocations should assume less — perhaps 5–6% nominal. Assuming conservatively and being pleasantly surprised is far better than the reverse, because the error only becomes visible when there is no time left to correct it.
More frequent compounding produces slightly more, but the effect is small at typical rates. Ten thousand dollars at 7% for 30 years yields about $76,100 compounded annually and about $81,200 compounded monthly — a 6% difference over three decades. Contribution rate and fees matter far more than compounding frequency.
No. In a tax-advantaged account such as a 401(k), IRA or Roth, growth is untaxed along the way and the projection is accurate. In a taxable brokerage account, dividends and realized gains are taxed annually, which reduces the effective return by roughly 0.5–1.5 percentage points depending on your bracket and turnover. For taxable accounts, reduce the return assumption accordingly.
Divide 72 by the annual return to approximate the years required to double your money. At 7% that is about 10.3 years; at 10%, about 7.2 years. It is a useful mental shortcut for evaluating claims quickly — anything promising to double your money in two years is implying a 40% annual return.
Historically, a lump sum invested immediately beats spreading it out roughly two-thirds of the time, because markets rise more often than they fall. Spreading it out is a behavioral hedge against regret rather than a mathematical improvement. Regular monthly contributions from income are a different thing entirely — that is simply investing as you earn, and it is the right default.
The next calculations that usually follow this one.
Your headline return is not your return. See what survives fees, taxes and inflation.
Find your target, see the gap, and check whether you are leaving employer money behind.
Your savings rate sets the date far more than your income does. This shows the year.
Translate future dollars into today's purchasing power — the adjustment most plans skip.
Work backwards from the number you need to the monthly amount that gets you there.
Guides that explain the decisions behind these numbers.
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