BedrockCalc — bedrockcalc.com
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Investment Calculator
Set a starting amount, a monthly contribution and a return, and this investment calculator shows how your money could grow — or flip it around and solve for the contribution, return or years a goal requires.
See how this works on a $1,000,000 goal — 3 real examples
Balance after 20 years
$0
You put in
$0
Investment growth
$0
Growth multiple
1.0×
Investment growth over time
Year-by-year growth scheduleDeposits, growth and ending balance each year
| Year | Deposits | Growth | End balance |
|---|
How your investment growth is projected
The projection uses the standard future-value identity that links every variable on this page:
FV = PV(1 + r)n + PMT · ((1 + r)n − 1) / r
where PV is the starting amount, PMT the monthly contribution, r the monthly return (annual rate ÷ 12), and n the number of months (years × 12). Growth compounds monthly and contributions are added each month; start-of-month deposits earn one extra period. The four “Solve for” modes simply rearrange the same equation to isolate whichever variable is unknown — the balance, the required contribution, the return, or the number of years — and the return solve uses a numerical root-finder, since it has no closed form. When a target can’t be reached at any steady return (for instance, a goal below what your inputs already produce), the calculator says so plainly rather than showing a misleading number.
The Today’s dollars view discounts each year’s balance by balance / (1 + i)years, where i is your assumed inflation rate, to show real purchasing power. These figures are projections based on a constant return and inflation rate, not a forecast — real markets vary year to year, so treat the output as a planning estimate.
Three routes to the same $1,000,000
The same goal solved three ways — for the monthly check, for the years, and for the return — starting from the page's $10,000.
Buying the goal with money: $1,842.13 a month
per month for 20 years$1,842.13
- The solver asks for $1,842.13 a month — $1,342.13 more than the $500 default plan saves.
- Total deposited on the way: $452,110. Compounding covers the other $547,890.
- Under half the million is money in; the account itself does the majority of the work.
A goal, a horizon and a rate pin the contribution down to the cent — no guessing.
Load this example (opens in a new tab)Buying the goal with time: 34 yrs 10 mo
at $500 a month34 yrs 10 mo
- Keeping the $500 habit means about 418 monthly deposits before the balance crosses seven figures.
- Money in comes to $219,000; growth contributes $783,852, more than three times the deposits.
- Nearly fifteen years longer than the $1,842 plan — the calendar covers what the paycheck doesn’t.
Time is the cheapest input: the smaller check gets there too, a decade and a half later.
Load this example (opens in a new tab)Buying the goal with risk: 15.36% a year
required annual return15.36%
- Reaching $1,000,000 in 20 years on $500 a month demands 15.36% a year, every year.
- That is roughly half again the stock market’s long-run average, sustained for two decades.
- A solved return this high is the calculator’s polite way of pointing at the other two tabs.
Of the three unknowns, the return is the one nobody controls — solve for it last.
Load this example (opens in a new tab)Illustrations only, not financial advice. Your own rate, taxes and insurance will differ — check with a qualified financial advisor before acting on any of this.
Making the most of your investment, in plain English
- Time beats timing. Doubling your years far more than doubles the growth, because the curve steepens as the balance compounds — starting ten years earlier usually beats contributing twice as much later.
- Contributions do the heavy lifting early. In the first decade most of your balance is money you put in; the crossover, where investment growth overtakes contributions, is what makes long horizons so powerful.
- Solve backward from a goal. Use the Monthly, Return or Years modes to answer “how much do I need to invest?” instead of guessing — far faster than nudging inputs until the balance matches.
- Watch the real number. A seven-figure future balance buys a lot less in 30 years; the Today’s-dollars toggle keeps your expectations honest.
- Be conservative with the return. The long-run stock average is ~10%, but any single decade can be far lower — modeling 6–8% leaves room for reality.
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Frequently asked questions
How much will my investment grow?
Enter your starting amount, monthly contribution, expected return and time horizon, and this investment calculator compounds them month by month. For example, $10,000 to start plus $500 a month at a 7% return grows to about $691,000 over 30 years — and only $190,000 of that is money you put in. The rest is compound investment growth.
How much should I invest each month to reach a goal?
Switch the “Solve for” toggle to Monthly and enter your target instead. The calculator works backward from the goal, starting amount, return and years to tell you the exact monthly investment required. You can just as easily solve for the return rate or the number of years you would need — the goal-based mode is the fastest way to reverse-engineer a plan.
What annual return rate should I assume?
It depends on where the money is invested. The U.S. stock market has averaged roughly 10% a year over the long run (about 7% after inflation), diversified bond portfolios return around 3–5%, and high-yield savings currently pay 4–5%. For planning many investors model 6–8% and treat anything higher as optimistic.
Does this investment calculator account for inflation?
Yes. Flip the “Dollars” toggle to Today’s dollars and the balance, chart and schedule are discounted by your assumed inflation rate, showing the real purchasing power of your future balance. A $500,000 nominal balance in 30 years is worth closer to $206,000 in today’s money at 3% inflation — a reminder that real investment return is what actually matters.
Should I contribute at the beginning or end of each month?
Beginning-of-month contributions earn one extra month of growth each, so they finish slightly ahead. Use the timing toggle to compare — on typical inputs the difference is under 1% of the final balance. Contributing consistently matters far more than the exact day.
What is the difference between total contributions and total interest?
Contributions (plus your starting amount) are the dollars you actually put in; interest is the compounded investment growth earned on top of them. In long horizons the interest portion usually dwarfs contributions — that crossover, where growth outpaces everything you deposited, is the whole point of investing early.
Disclaimer: these calculators are educational tools, not financial advice. They model your inputs with published formulas, but they cannot know your full situation — for decisions with real stakes, talk to a qualified professional. Formulas and defaults last reviewed .