Compound Return Simulator

Visualise how compounding grows your principal at a target return, and map out your asset growth path.

Initial principal

KRW

Extra contribution per period (optional)

KRW

Target return

Period

Compounding interval

Final simulated asset value

Total principal (cumulative)0

Net compound gain0

📊 Period-by-period growth report

Period	Start balance	Contribution	Gain	End balance

What this tool does

Enter an initial amount, a contribution added every period, a target return per period and a duration, and this simulator works out the final value, total principal invested and pure compound gain, with a growth curve and a period-by-period table. You choose monthly or daily compounding. Use it to plan regular investing or to see how compounding grows with time. Amounts are in Korean won.

How it is calculated

The key point is that the return you enter is per period, not per year. With monthly compounding that rate is applied every month; with daily compounding, every day. Each period the contribution goes in first, then (previous balance + contribution) × rate is added as gain to give the closing balance. This repeats for the chosen number of periods, and final balance minus total paid in is shown as the compound gain. For example, 10,000,000 won up front, 500,000 a month, 1% a month for 24 months gives total principal of 22,000,000, a final value of about 26,320,000 and a gain of about 4,320,000. The default is 5% a month, so the same inputs show about 55,610,000, but 5% a month nearly doubles money in a year (about 1.8 times), a very aggressive assumption. If you think in annual returns, convert to a monthly figure: 6% a year is roughly 0.5% a month.

Enter the initial amount in won; 0 is fine if you will only contribute

Enter the contribution per period (optional)

Enter the target return per period (%) and the duration, in months for monthly compounding or days for daily

Choose monthly or daily compounding with the buttons; it recalculates at once

Check the final value, principal, gain, chart and table, and download the table as a spreadsheet file if needed

Things to know

Entering an annual return in the rate field makes results absurdly large. For monthly compounding, divide the annual rate by about 12.

Contributions go in at the start of each period and earn that period's return immediately, so results are slightly higher than if they went in at the end.

Compounding responds more to time than to rate. Change only the duration to see why starting early and staying invested helps.

Real returns rise and fall and some years lose money, so balances do not grow at the same rate every period. The result shows what happens if the assumption holds exactly.

Taxes, fees and inflation are not deducted. Over long periods small cost differences matter a lot, so try a lower rate for real planning.

The download creates the file in your browser and saves it directly; your inputs are not sent to a server.

Frequently asked questions

Is the rate in the compound calculator an annual rate?

No. It is the rate per chosen period: a monthly rate for monthly compounding, a daily rate for daily. For 6% a year, enter about 0.5% a month.

How much does 1% a month grow in a year?

Without contributions, 10,000,000 becomes about 11,270,000 after 12 months, roughly 12.7% growth. That it beats simply adding 1% twelve times (12%) is the compounding effect.

When do contributions go in?

At the start of each period, earning that period's return straight away. The table's contribution column shows the amount added in each period.

Does it tell me whether a return is realistic?

No. Past returns are only a reference and guarantee nothing, and high assumed returns overstate results. Compare with a conservative figure too.

This is the product of your assumptions, not investment advice or a guarantee of returns.