以下のガイドはまだ日本語に翻訳されていないため、英語で表示しています。計算機自体はすべて日本語に対応しています。
この計算機の使い方
- Choose what to solve for: the monthly payment or the payoff time.
- Enter the loan balance and the annual interest rate.
- Enter either the loan term in years or the monthly payment you can afford.
- Review the amortization schedule to see how each payment splits between principal and interest.
計算式
For a fixed term, the payment uses the amortization formula. For a fixed payment, the number of months n is solved from the same equation using logarithms. The payment must be larger than the first month's interest (L × r), or the loan never amortizes.
Payment = L × r / (1 − (1 + r)^−n)
n = −ln(1 − r × L / Payment) / ln(1 + r)
Example
- Balance $25,000 at 7.5% with a $600 monthly payment: r = 0.00625.
- n = −ln(1 − 0.00625 × 25,000 / 600) / ln(1.00625) ≈ 48.4 months.
- So the loan is repaid in 49 payments, with a smaller final payment.
よくある質問
What happens if my payment is too low?
If the payment doesn't exceed the monthly interest, the balance never goes down. The calculator will tell you when that happens.
Why is the last payment smaller?
When you choose a fixed payment, the final payment is only what is needed to clear the remaining balance.
Can I use this for credit cards?
Yes, as an approximation. For card-specific details such as minimum payments, use the credit card payoff calculator.