Compound Interest Calculator With Monthly Contributions
Estimate how a starting balance and monthly deposits could grow with compound interest. Enter your assumptions once, compare compounding frequencies, and review the year by year path behind the final number.
A lot of finance pages misuse contribution math by pretending every monthly deposit compounds for the full period. This tool converts the monthly budget into equal deposits per compounding period. That is exact for its stated schedule; use monthly compounding for actual monthly deposits. Other frequencies use a grouped-deposit approximation.
Extra outputs people usually need
Balance path chart
The bars show the total projected balance by year. It is intentionally simple so the trend stays readable on mobile.
Scenario comparison
Keep the same starting amount, years and monthly deposit, then compare different return assumptions.
| Annual return | Final value | Total interest |
|---|
How to read the result
The balance at the end of the time period using the assumptions above.
Your starting amount plus all recurring deposits. This is the amount you actually put in.
The gap between final value and total contributions. This is the compounding effect in money terms.
Beginning of period gives each deposit more time to grow, so it usually produces a slightly higher result.
Year by year breakdown
This table exists because users trust projections more when they can see the path, not just a single big number.
| Year | Ending balance | Total contributed | Total interest |
|---|
What matters most in compound growth
Methodology and assumptions
- Constant annual return. This calculator assumes the rate stays the same for the full period. Real markets do not move in a straight line.
- No taxes or fees included automatically. If you are using taxable accounts or products with charges, lower the return assumption manually.
- Recurring deposits are spread into the chosen compounding schedule. This is a grouped-deposit approximation when the selected frequency is not monthly.
- Educational estimate only. Use it for planning, comparison and intuition. Do not treat it as personal financial advice.
For more detail, read how CompoundCalc handles calculations.
Best supporting pages
FAQ
Why can daily compounding look only slightly better than monthly compounding?
Because time, contribution size and annual return normally dominate the result. Frequency matters, but often by less than beginners expect.
Should I choose beginning or end of period?
Choose beginning of period if the money is invested sooner. End of period is a more conservative default and often matches monthly saving habits.
Does this include inflation?
The main balance is nominal. The Today’s dollars output applies the inflation assumption separately. Use the inflation guide to understand purchasing power; do not also subtract inflation from the rate when using the Today’s dollars output.
Is this calculator good for retirement planning?
It is useful as a planning estimate. For retirement-specific questions, combine it with the retirement compound interest calculator, the 4 percent rule calculator and your own fee and tax assumptions.