Result
Lasts for
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This calculation is for informational purposes only and does not replace advice from a qualified professional. Formulas and rates may not fit your exact situation — double-check the figures before making decisions.
How it is calculated
If the monthly withdrawal doesn't exceed the interest accrued on the balance that month (balance × monthly rate), the deposit never shrinks — you can withdraw that amount indefinitely without touching the principal.
If the withdrawal exceeds the interest, how many months the deposit lasts = ln(withdrawal ÷ (withdrawal − balance × monthly rate)) ÷ ln(1 + monthly rate). This is the same math as loan term from a given payment, just in reverse: there a payment shrinks debt, here a withdrawal shrinks a deposit.
The calculation assumes a constant rate and withdrawing exactly the same amount every month. If the bank's rate changes over time or withdrawals are irregular, the actual duration will differ from the estimate.