Compounding Calculator
See how your capital grows when profit is reinvested and a fixed amount is added every month.
Results
Enter your figures and the result appears here.
- Portfolio value
- Total invested
| Year | Opening | Added this period | Closing | Total invested | Total profit | Total gain % |
|---|
How this is calculated
The gain percentage you enter applies to a whole period, but money arrives every month. The calculator therefore converts that period rate into its equivalent monthly rate and compounds month by month. That is why setting Monthly Investment to 0 returns exactly what a plain compounding calculator would give you — twelve months of the equivalent monthly rate come back to the annual gain you typed in.
Deposit timing matters. Start of month means the money goes in first and then earns a full month of growth. End of month applies growth to the existing balance first and adds the deposit afterwards, so every deposit gets one month less working time. With everything else held equal, Start of month produces a slightly higher final balance.
“Total gain %” divides profit by the total amount invested — the starting balance plus every monthly deposit that followed. Measuring the gain against the starting balance alone would flatter the result, because it ignores all the money added later.
Disclaimer: This tool is for illustration only. Market returns are not the same in every period; this calculator assumes a fixed rate and excludes brokerage, taxes and inflation. This is not investment advice.