An initial balance only
With no further deposits, 1,000 at 10% nominal interest for one year becomes 1,100 with annual compounding and about 1,104.71 with monthly compounding.
Explore a constant nominal rate, a compounding frequency, and level monthly contributions. Negative assumed rates model smooth losses; actual investment paths vary.
USD 17,175.24Ending nominal balance
USD 13,000.00Total contributed
USD 4,175.24Growth / loss
5.1162%Effective annual rate
Monthly schedule
Calculated at full precision; displayed amounts are rounded. CSV includes every period with six decimal places.
| Month | Opening | Interest / growth | Contribution | Closing |
|---|---|---|---|---|
| 1 | USD 1,000.00 | USD 4.17 | USD 100.00 | USD 1,104.17 |
| 2 | USD 1,104.17 | USD 4.60 | USD 100.00 | USD 1,208.77 |
| 3 | USD 1,208.77 | USD 5.04 | USD 100.00 | USD 1,313.80 |
| 4 | USD 1,313.80 | USD 5.47 | USD 100.00 | USD 1,419.28 |
| 5 | USD 1,419.28 | USD 5.91 | USD 100.00 | USD 1,525.19 |
| 6 | USD 1,525.19 | USD 6.35 | USD 100.00 | USD 1,631.55 |
| 7 | USD 1,631.55 | USD 6.80 | USD 100.00 | USD 1,738.34 |
| 8 | USD 1,738.34 | USD 7.24 | USD 100.00 | USD 1,845.59 |
| 9 | USD 1,845.59 | USD 7.69 | USD 100.00 | USD 1,953.28 |
| 10 | USD 1,953.28 | USD 8.14 | USD 100.00 | USD 2,061.42 |
| 11 | USD 2,061.42 | USD 8.59 | USD 100.00 | USD 2,170.01 |
| 12 | USD 2,170.01 | USD 9.04 | USD 100.00 | USD 2,279.05 |
To align monthly deposits with any compounding frequency, monthly growth is (1 + annual rate ÷ frequency)^(frequency ÷ 12) − 1. This smooth fractional-period convention may differ from an account that credits interest only on specific dates. Daily uses 365 periods; leap days are excluded.
Your inputs and calculations stay in this browser. No live financial data is fetched; amounts use your selected USD or GBP labels.
How to use the Compound Interest Calculator
- 01
Enter an initial amount, a monthly contribution, and an assumed nominal annual rate.
- 02
Choose the duration, compounding frequency, and contribution timing.
- 03
Review effective annual growth and the balance chart, then copy the summary or export all months.
Examples
Deposits at a zero rate
An initial 1,000 plus 100 per month for ten years at 0% becomes 13,000. All growth comes from contributions; interest is zero.
Nominal and effective annual rates
The nominal annual rate is split across the selected number of compounding periods. The effective annual rate describes the result of a full year of that compounding. A positive nominal rate compounded more often generally has a higher effective rate than the same rate compounded once per year.
Aligning deposits with compounding
Deposits happen monthly even when compounding is annual, quarterly, or daily. The calculator uses an equivalent monthly growth factor of (1 + r/m)^(m/12), where r is the nominal decimal annual rate and m is periods per year. This fractional-period convention provides a smooth scenario rather than reproducing every account-crediting rule.
Reading growth and loss
Total contributions include the initial balance and every monthly deposit. Growth or loss is ending balance minus that contribution total. Negative assumed rates are accepted down to −99%; they create a smooth decline rather than simulating a volatile sequence of market returns.
What to know
- Constant-rate scenario only; no live rates, price predictions, taxes, or fees.
- Monthly schedules are limited to 100 whole years and results above the calculation ceiling are rejected.
Common questions
Does daily compounding follow calendar dates?
No. Daily means 365 compounding periods per modeled year. Leap days, business-day adjustments, and actual deposit dates are not included.
Why do start-of-month deposits grow more?
Each receives the month’s growth immediately after being deposited; an end-of-month deposit starts earning modeled growth in the following month.
Are the results inflation adjusted?
No. These are nominal balances. Taxes, fees, and changing purchasing power can reduce the value available to spend.