信用卡还清计算器 — 公式
## How Credit Card Payoff Is Calculated
The number of months to pay off is:
**n = -log(1 - r × B / P) / log(1 + r)**
Where B = balance, P = monthly payment, r = monthly interest rate. Your payment must exceed the monthly interest charge (B × r) or the balance will never decrease.
The number of months to pay off is:
**n = -log(1 - r × B / P) / log(1 + r)**
Where B = balance, P = monthly payment, r = monthly interest rate. Your payment must exceed the monthly interest charge (B × r) or the balance will never decrease.
计算示例
$5,000 balance at 22% APR with $200 monthly payment.
- Monthly rate = 22% / 12 = 1.833%
- Months = -log(1 - 0.01833 × 5000 / 200) / log(1.01833)
- = -log(1 - 0.4583) / log(1.01833)
- = -log(0.5417) / 0.01817 = 33.7 → 34 months
- Total paid = 34 × $200 = $6,800
- Total interest = $6,800 - $5,000 = $1,800