Enter your starting amount, monthly contributions, rate of return, and compounding frequency to see your future balance — plus how much of it came from your own contributions versus growth.
This calculator projects how your savings or investments grow when interest compounds on top of interest. Add regular monthly contributions to see how consistent saving accelerates growth over time.
Compound interest means you earn returns not just on your original contributions, but on the growth those contributions already earned. Over long time periods, this creates accelerating growth — the later years typically add more to your balance than the earlier ones, even with the same contribution amount.
More frequent compounding produces slightly higher returns at the same stated annual rate, though the difference is usually small compared to the impact of your rate of return and time horizon.
| Frequency | Effect on growth |
|---|---|
| Annually | Baseline — interest is added once per year |
| Quarterly | Slightly higher than annual over time |
| Monthly | The most common structure for savings and investment accounts |
| Daily | Marginally higher still, common for some savings accounts |
Beelinger compounds your starting amount at your chosen frequency using the standard compound interest formula, then adds your monthly contributions with their own growth over the remaining time period. Total growth earned is your future balance minus your starting amount and every contribution you made. This is a projection based on a steady average rate — actual returns on invested money fluctuate year to year.
Use these related tools to find money to invest and make sure your foundation is solid before you commit to a longer time horizon.
Beelinger's Money Coach can help you figure out how much you can realistically contribute each month and what that means for your long-term plan.
Compound interest is interest calculated on both your original contributions and the interest those contributions have already earned. Over time, this produces accelerating growth compared to simple interest, which only applies to your original amount.
Yes, but usually only slightly. Daily or monthly compounding produces marginally higher returns than annual compounding at the same stated rate. Your rate of return and time horizon matter far more than compounding frequency.
The Rule of 72 is a quick way to estimate how long it takes an investment to double: divide 72 by your annual rate of return. At 7%, for example, your money doubles roughly every 10.3 years.
Simple interest is calculated only on your original amount every period. Compound interest is calculated on your original amount plus all previously earned interest, which is why compound growth accelerates over long time periods.
There's no required minimum for most modern investment accounts. This calculator shows that consistent monthly contributions, even small ones, can matter more over a long time horizon than a large starting amount.