Calculator guide
How should you read recurring investment results?
The same monthly contribution can produce very different ending balances as return and time change. If you start with a goal, you can also work backward to the monthly contribution or time required.
Ending balance
Separate total contributions from investment gain, then compare how return differences widen over time.
Contribution needed
Set a goal and deadline to calculate the monthly contribution required at each return.
Time to goal
Keep the monthly contribution fixed, then compare the time needed at each return.
How is recurring investment calculated?
The calculator divides the entered annual return by 12, applies that monthly return to the existing balance, and then adds the same contribution at each month-end. A new contribution starts earning a return in the following month.
The ending balance is the sum of monthly contributions and accumulated investment gain. Required contributions are rounded up so the goal is not missed, and time to goal is rounded up to the first month in which the balance reaches the target.
When should you use each of the three modes?
Use ending balance when you already know how much you can contribute and for how long. Use monthly contribution when the goal amount and deadline are fixed and you need to work backward to a saving target.
Use time to goal when your current contribution is fixed and you want to estimate the timeline. Each mode compares several return scenarios side by side, so it is most useful for reading a range rather than relying on one forecast.
What should you be careful about?
The entered annual return is a simplified assumption that repeats at a constant monthly rate. Real investments can include losses, changing returns, missed contributions, taxes, and fees.
Inflation is also excluded, so the future purchasing power of a long-term target should be checked separately. The result is a planning comparison, not a return guarantee or investment advice.