1. Enter the starting balance
Use the amount already invested or enter zero when the plan starts with monthly contributions only.
Investing
Compound interest and future value calculator
Estimate how an initial amount and regular monthly contributions may grow over time. Change the rate, term and currency to compare scenarios.
Estimated future value
$106,639
Your contributions
$70,000
Estimated return
$36,639
Effective annual rate
7.229%
Growth over time
1: $16,919.191 · $16,919.19
2: $24,338.582 · $24,338.58
3: $32,294.313 · $32,294.31
4: $40,825.164 · $40,825.16
5: $49,972.705 · $49,972.70
6: $59,781.536 · $59,781.53
7: $70,299.437 · $70,299.43
8: $81,577.688 · $81,577.68
9: $93,671.229 · $93,671.22
10: $106,639.0210 · $106,639.02
110
Hover, tap or focus a column to see its exact value.
Monthly growth schedule
Detailed values use the same assumptions as the summary above.
| Month | Starting balance | Contribution | Return for month | Ending balance |
|---|---|---|---|---|
| 1 | $10,000.00 | $500.00 | $58.33 | $10,558.33 |
| 2 | $10,558.33 | $500.00 | $61.59 | $11,119.92 |
| 3 | $11,119.92 | $500.00 | $64.87 | $11,684.79 |
| 4 | $11,684.79 | $500.00 | $68.16 | $12,252.95 |
| 5 | $12,252.95 | $500.00 | $71.48 | $12,824.43 |
| 6 | $12,824.43 | $500.00 | $74.81 | $13,399.24 |
| 7 | $13,399.24 | $500.00 | $78.16 | $13,977.40 |
| 8 | $13,977.40 | $500.00 | $81.53 | $14,558.93 |
| 9 | $14,558.93 | $500.00 | $84.93 | $15,143.86 |
| 10 | $15,143.86 | $500.00 | $88.34 | $15,732.20 |
| 11 | $15,732.20 | $500.00 | $91.77 | $16,323.97 |
| 12 | $16,323.97 | $500.00 | $95.22 | $16,919.19 |
This is an illustrative calculation, not a forecast or financial advice. Actual returns may vary.
Detailed guide
Compound interest, future value and regular contributions
Compound interest adds each period’s return to the balance, so later returns are earned on both the original principal and earlier interest. This calculator combines that effect with a starting balance and equal monthly contributions.
Choose daily, monthly, quarterly, semiannual, annual or continuous compounding and decide whether contributions arrive at the beginning or end of each month. Use a net rate if you want the scenario to reflect expected fees and taxes.
How to use the compound interest calculator
2. Set contributions and rate
Enter a monthly contribution, nominal annual rate and the compounding frequency that matches the account or scenario.
3. Compare time horizons
Change one assumption at a time and compare your contributions with the interest portion of the result.
Compound interest formula with contributions
FV = P(1 + r)ⁿ + PMT × ((1 + r)ⁿ − 1) ÷ r
P is the starting principal, PMT is the monthly contribution, r is the effective monthly rate and n is the number of months. Beginning-of-month contributions receive one additional month of growth.
The calculator converts the entered nominal annual rate and compounding frequency into an equivalent monthly rate. Continuous compounding uses the exponential equivalent.
Compound growth example
With $10,000 initially, $500 contributed at the end of every month, a 7% nominal rate compounded monthly and a 10-year term, total contributions are $70,000. The result separates those contributions from the estimated compound return.
What changes the result
Compounding frequency
More frequent compounding raises the effective annual rate when the same nominal rate is used. Compare products on the same APY or effective-rate basis.
Contribution timing
A beginning-of-month contribution compounds for one month longer than an end-of-month contribution. That difference accumulates over long terms.
Constant-rate limitation
Market returns and variable account rates do not arrive evenly. Use conservative, base and optimistic scenarios instead of treating one rate as a forecast.
Decision guide
How to test a compound-growth scenario
The leading Google pages explain compounding, contribution timing, formulas, and result interpretation. A useful projection should separate money you contribute from growth generated by the assumed return, then test how sensitive the ending balance is to time and rate.
Compounding and contributions do different work
Compounding keeps prior earnings in the balance so they can earn a return in later periods. Contributions are new principal. Review both totals separately: a large ending balance can come mainly from disciplined saving rather than investment growth, and that distinction matters when you judge whether a plan is realistic.
Match the rate and compounding period
An annual rate compounded monthly is converted to a periodic rate before each calculation. A product quoting APY has already incorporated its compounding convention, while a nominal rate may not have. Avoid applying monthly compounding to an APY without converting the assumption, because that can count the effect twice.
Run a range instead of trusting one forecast
Keep the starting balance, contribution, and term fixed while testing a lower, central, and higher return. The spread shows how much the goal depends on market performance. For a long horizon, also compare the nominal result with its purchasing power after inflation, fees, and taxes.
Projection checklist
- Confirm when contributions are made.
- Use a rate consistent with the compounding setting.
- Separate contributions from earnings.
- Stress-test a lower-return case.
How to compare scenarios
Save a baseline, then change only one input at a time: amount, rate, term, or recurring payment. Record the supporting outputs as well as the headline result—contributions, interest, total cost, remaining balance, or target date. This isolates the assumption that actually changes the decision instead of hiding it inside several simultaneous edits.
Do not tune every assumption until the calculator produces a preferred answer. Start with a cautious case, follow with a central case, and treat the favorable case as an upside scenario. A calculator result is not a lender quote, market forecast, or tax determination; actual dates, rounding, fees, contract rules, and required payments must be checked in primary documents.
Keep enough precision in the inputs and round only the output used for a decision. If the estimate supports a transaction, loan, tax calculation, or long-term plan, repeat it with figures from the contract or official statement. Any difference helps identify the assumption that still needs verification.
Compound interest questions
What is the difference between compound and simple interest?
Simple interest is calculated only on principal. Compound interest also earns a return on interest credited in earlier periods.
Does currency change the formula?
No. Currency changes formatting only; the growth formula is the same.
Is APY the same as the entered nominal rate?
Not necessarily. APY already includes compounding, while a nominal rate needs a compounding frequency. The calculator displays the effective annual equivalent.
Are fees, taxes and inflation included?
No. Reduce the entered return to model fees or taxes, and use a real return if you want to account for inflation.
Updated: July 28, 2026
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