Estimate your ending balance, interest earned, and total contributions over time. Supports recurring contributions, compounding frequency, and contribution timing.
- Enter your starting balance: This is the amount you have today (your initial deposit).
- Enter your contribution amount: This is how much you add each time you contribute. Set it to 0 if you will not add anything.
- Enter years to grow: How long you plan to leave the money invested or saved. Decimals are OK (example: 7.5).
- Enter the annual rate: Your expected average return per year (percent). This is an estimate.
- Open Advanced options (optional): Change contribution frequency (monthly, weekly, etc.), compounding frequency, and whether contributions happen at the beginning or end of each period.
- Click Calculate: Review the ending balance, interest earned, and the balance-by-year chart. Use “More details” for the breakdown.
This calculator estimates how a balance can grow when you start with an initial amount and then add a fixed contribution on a schedule. It assumes a fixed annual rate and applies it evenly over each contribution period.
You enter a nominal annual rate (the percent per year) and choose a compounding frequency. The calculator converts that nominal rate into an effective annual yield (an APY-style estimate) using:
The output label “Effective annual yield (APY estimate)” is meant as a plain-language way to show how compounding changes the same nominal rate. For deposit accounts in the US, “APY” is defined and calculated under Regulation DD (Truth in Savings), with a standard method for annualising compounded returns.
Contributions can be monthly, weekly, biweekly, or yearly. The calculator converts the effective annual yield into a per-contribution-period rate:
This is an approximation that keeps the same effective annual yield while spreading growth across the chosen contribution schedule.
The calculator runs a step-by-step simulation for N contribution periods, where: N is rounded to the nearest whole period based on your “Years to grow” and contribution frequency.
- “Beginning of period” gives each contribution one extra period of growth (often called an “annuity due” setup in finance textbooks).
- “End of period” means the contribution is added after that period’s interest is applied (often called an “ordinary annuity” setup).
- Total contributions = C multiplied by the number of contribution periods.
- Total principal (your money) = starting balance + total contributions.
- Interest earned = ending balance – total principal.
If you enter a rate range, the calculator runs two extra simulations: one at (rate minus range) and one at (rate plus range), with rates floored at 0% and capped at 100%. This is a simple “what if” sensitivity check, not a probability forecast.
The chart plots the projected balance at yearly checkpoints. The dashed gray line is your starting balance. This chart is meant to show the shape of growth over time, not day-to-day movement.
- Assumes a constant rate and constant contribution amount.
- No taxes, fees, contribution limits, withdrawals, or minimum balance rules.
- “Daily” compounding uses m = 365 as a standard estimate; real institutions can differ in how they apply daily accrual and posting.
- “Years to grow” is converted into a whole number of contribution periods using rounding, so very small changes in years can change N by 1 period.