Loan Repayment Calculator

This is relevant to credit cards (daily), lines of credit (monthly), and some types of loans (monthly/amortized).

Source Code

Information

Principal: original loan value; Annualized rate: interest charged per year (usually just called the "interest rate" of the loan); Amortization: fixed time period over which the loan is repaid (e.g., mortgage); Average payment: average payment per period

This calculator assumes monthly statements are given. If interest is charged daily, it is added daily to the balance. If it is charged monthly, it is only added on the first day of the next month. In this case, the interest shown in the table is not truly realized until the next statement period.

Credit Card (charged daily)

Mortgage (amortized, charged monthly)

Line of Credit and Other Loans (charged monthly)

Definitions for the formulae used in these calculations

$P_{n}$ : Payment for period n ($)

$B_{n}$ : Starting balance for period n ($) (previous month ending balance)

$I_{n}$ : Interest for period n ($)

$ℳ$ : Minimum payment multiplier (%) (e.g., 4.5% => M=1.045)

$d_{prd}$ : Days in the period (e.g., biweekly => d=14)

$r_{ann}$ : Annualized rate (%) (e.g., 5% => r=0.05)

Period Payment: $P_{n} = ℳ \times B_{n-1} + I_{n}$

Period Interest (Charged monthly): $I_{n} = B_{n-1} (\frac{d_{prd} r_{ann}}{365.25})$

Period Interest (Charged daily): $I_{n} = B_{n-1} ((1 + \frac{r_{ann}}{365.25}) - 1)^{d_{prd}}$

Principal Amount ($) Annualized Rate (%) Payment Frequency (/yr) Average Payment ($) Minimum Payment Method Amortization (yr) Down Payment ($)

Interest Charged Monthly

Interest Charged Daily

First Payment Date

Last Payment Date

Total Paid ($) % of Total as Interest Total Interest ($) # Payments to $0 Balance Years to $0 Balance