Investment Calculator
Estimate how much your investment could grow with regular contributions and compound returns.
Example
Start with $10,000, add $500/month for 10 years at a 7% annual return compounded monthly.
You contribute $10,000 + ($500 x 120) = $70,000 total. The projected ending balance is about $106,639.02, meaning roughly $36,639.02 comes from compound interest.
How it works
Enter a starting amount, a recurring contribution, the number of years and your expected annual return, then pick how often it compounds. The tool projects your ending balance and splits it into money you put in versus interest earned.
Good to know
This Investment Calculator projects the future value of a portfolio you build over time by combining a one-time starting amount with steady recurring contributions and a fixed annual return. It is aimed at anyone modeling a long-term savings goal — retirement, a house down payment, a college fund — who wants to see how much of the final balance comes from money they deposited versus money the returns generated. You set a starting amount, a monthly or annual contribution, the number of years, an expected annual return, and a compounding frequency, and it returns an ending balance broken into total contributed and interest earned.
Reach for it when you want to compare scenarios rather than nail down a single number: how the ending balance shifts if you contribute $500 instead of $300 a month, stretch the horizon from 10 to 20 years, or assume a more conservative 5% return instead of 7%. Because every input recalculates instantly in your browser, it is well suited to side-by-side what-if testing before you commit to a contribution schedule.
To read the result, focus on the split between the two stat boxes and the comparison bars. The "Total contributed" figure is your own cash (starting amount plus every deposit), and "Interest earned" is everything the ending balance adds on top. Early on, contributions dominate; over long horizons the interest bar grows and can eventually exceed what you put in, which is the visible effect of compounding. One mechanical detail to note: contributions are assumed to be made at the end of each period, so a real plan with deposits at the start of each month would finish slightly higher.
Keep in mind this is a nominal, pre-tax projection that assumes a single constant return every year. Real markets fluctuate, and a 7% average return rarely arrives as a smooth 7% annually, so treat the output as a planning estimate rather than a forecast. To gauge purchasing power, subtract an inflation assumption (often 2-3%) from your return before calculating.
Frequently asked questions
Does this account for inflation or taxes?
No. The result is a nominal projection before taxes and inflation. To approximate real (inflation-adjusted) growth, subtract your expected inflation rate (e.g. 2-3%) from the annual return before calculating.
How does the compounding setting change my result?
Compounding determines how often returns are reinvested. More frequent compounding (monthly vs annually) slightly increases the ending balance for the same annual rate. Your contribution amount is preserved per year regardless of the compounding choice.
Is my data uploaded anywhere?
No — this calculator runs entirely in your browser; nothing is uploaded.
Is this financial advice?
No. These are educational estimates — consult a qualified financial professional before making decisions.
People also ask
What is a realistic annual return rate to use in an investment calculator?
Many people use a long-run figure in the range of roughly 5% to 8% for a diversified stock-and-bond portfolio, with lower numbers for bond-heavy mixes and higher ones for all-stock. Past averages do not guarantee future results, so it is common to run both an optimistic and a conservative rate to see the range of outcomes.
Does increasing my monthly contribution or extending the time horizon matter more?
Both help, but time tends to amplify the effect of compounding because contributions made earlier have more years to grow. Raising the contribution increases the principal you put in, while adding years increases how much interest that principal can accumulate; testing both in the calculator shows which lever moves your ending balance most for your situation.
Why is my interest earned lower than I expected for a high return rate?
Recurring contributions are added gradually over the period, so each dollar only earns returns for the time remaining, not the full horizon. The starting amount compounds for all years, but a deposit made in year nine has had little time to grow, which keeps the total interest lower than a simple rate-times-years estimate would suggest.
What is the difference between the return rate and the compounding frequency?
The return rate is the total annual percentage your investment earns, while the compounding frequency is how often that return is applied and reinvested within the year. For the same annual rate, more frequent compounding (monthly versus annually) produces a slightly higher ending balance because earnings start earning sooner.
How can I estimate the inflation-adjusted value of the projected balance?
One common approach is to subtract an expected inflation rate, such as 2-3%, from your annual return before running the calculation, which yields a rough real (purchasing-power) growth figure. The result is still an estimate, since actual inflation varies year to year.
Can I use this calculator for a Roth IRA, 401(k), or brokerage account?
The math is the same for any account that earns a return on contributions, so you can model any of them by entering your balance, deposits, and assumed return. The calculator does not account for account-specific contribution limits, employer matches, or tax treatment, so those would need to be considered separately.
Why does my ending balance change when I switch between monthly and annual contributions?
Switching frequency changes how your deposits are timed across the year, which affects how long each contribution compounds. The tool preserves the same yearly total, but spreading it monthly versus depositing it once a year can produce a slightly different ending balance depending on the compounding setting.
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