Quick guide
How to use this calculator
- Enter one scenario using a consistent currency and the periods shown by each label.
- Keep targets, coverage time, income basis, and expected return aligned with your own planning definition.
- Read the result with the visible assumptions before using it in a financial decision.
Calculation method
Calculation method
With end-of-month contributions, target = current savings × (1+r)^n + contribution × ((1+r)^n−1)/r, using the n-month zero-rate limit when r = 0.
Exact decimal/rational arithmetic is used for cash-flow totals. The savings-goal projection uses stable logarithmic compounding with a zero-rate limit and rejects overflow or a nonzero result that would become zero. Repeating ratios use parentheses; an ellipsis marks a preview longer than 12 decimal places.
Worked example
Worked example
A 12,000 target from zero current savings over 12 months at 0% requires 1,000 at the end of each month.
With end-of-month contributions, target = current savings × (1+r)^n + contribution × ((1+r)^n−1)/r, using the n-month zero-rate limit when r = 0.
Supported inputs
Precision and limits
Visible input limits
Amounts accept up to 30 digits and 12 decimal places and are capped at 1e12. Rates are capped at 1000%; whole-month horizons are capped at 1,200, with 120 months for reserve coverage and sabbatical duration.
International scope
No currency, country, benefit system, recommended fund size, guaranteed return, or savings-rate standard is assumed.
Planning boundary
Results are deterministic projections of entered assumptions, not guarantees, investment advice, or a judgment about an adequate reserve.
Calculator-specific assumptions
Contributions occur at each month-end and the entered nominal annual return is divided by 12. Actual savings or investment returns, fees, taxes, and timing can differ.