Quick guide
How to use this calculator
- Enter one scenario with a consistent currency and the exact time basis shown by each label.
- Treat growth, return, price change, and future contributions as assumptions rather than forecasts.
- Use the component results and calculator-specific boundary to interpret the primary answer.
Calculation method
Calculation method
First-year annual cost is 12 × monthly subscription total; each later year changes by the entered constant annual percentage and cumulative cost is the finite geometric sum.
Exact rational arithmetic is used where no compounding is needed. Bounded projections use stable logarithmic growth, deliberate decimal display rounding, overflow checks, and explicit unreachable states; a nonzero result is never replaced by zero.
Worked example
Worked example
A monthly total of 100 with 0% annual price change costs 1,200 per year and 6,000 over 5 years.
First-year annual cost is 12 × monthly subscription total; each later year changes by the entered constant annual percentage and cumulative cost is the finite geometric sum.
Supported inputs
Precision and limits
Visible input limits
Amounts accept up to 30 digits and 12 decimal places and are capped at 1e12. Annual change is −100% to 1000%; projections use at most 100 years or 1,200 months, and a no-spend challenge at most 3,650 days.
International scope
No currency, tax, inflation rate, wage path, market return, withdrawal rule, price database, or recommended spending standard is assumed.
Projection boundary
Long-range results are deterministic illustrations of entered assumptions, not forecasts, guarantees, financial advice, or value judgments about spending and work.
Calculator-specific assumptions
The monthly amount is assumed constant within each year and changes once between years. Cancellations, new subscriptions, billing cycles, taxes, exchange rates, and discounts are excluded.