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How to Calculate Interest on a Loan

Interest calculation is a foundational aspect of lending, directly influencing borrower payments and the loan’s overall cost. From simple interest for short-term loans to advanced amortization schedules with custom adjustments, understanding each calculation method is essential for loan servicers and lenders. 

Nortridge Loan System (NLS) simplifies these processes, automating interest calculations and adapting to the unique needs of each loan structure. This guide provides a step-by-step look at various calculation methods for figuring interest on a loan, demonstrating how NLS streamlines complex computations and ensures accuracy across loan portfolios.

Understanding the Basics of Interest Calculation

Calculating interest rate on a loan begins with three primary components:

Principal

The amount borrowed at the outset. As the foundation for interest calculation, the principal amount affects all aspects of the loan’s cost.

Interest

The fee lenders charge for borrowing funds, expressed as a percentage of the principal.

Rate

The annual percentage rate (APR) applied to the principal. This rate determines the total interest a borrower will pay over the loan term.

Together, these components create the framework for calculating different types of interest. Nortridge simplifies this process by allowing servicers to easily track and adjust these elements, facilitating accurate and efficient interest management across diverse loan types.


The Simple Interest Method

Simple interest calculates interest solely on the original principal, making it a straightforward approach for short-term loans where interest remains consistent throughout.

Formula:

Example:
For a $10,000 loan with a 5% annual rate over 3 years:

The total interest paid over 3 years would be $1,500, making the total amount owed $11,500.

Application in Nortridge

Nortridge automates simple interest calculations, allowing servicers to set the loan’s principal and rate. This saves time, reduces errors, and supports straightforward payment schedules ideal for auto loans, personal loans, and short-term financing.


Fixed Amortization

Fixed amortization combines interest and principal into consistent, equal payments, gradually reducing the loan balance over time. This is especially common in mortgages and installment loans, where borrowers benefit from stable monthly payments.

Formula for Monthly Payment: 

Example:
For a $10,000 loan at a 5% annual interest rate over 3 years (36 months):

How Nortridge Automates Amortization

NLS automates fixed amortization schedules, calculating equal payments that reduce both interest and principal over time. This ensures consistency and accuracy, helping servicers manage loans efficiently and reliably.


Add-On Interest and the Rule of 78s

Add-on interest calculates total interest at the beginning of the loan, applying it to the original principal for the entire term. Often paired with the Rule of 78s, this method allocates more interest to early payments.

Formula for Add-On Interest: 

Example:
For an $11,025 loan at 8.8435% over one year:

The Rule of 78s, applied to add-on interest loans, distributes higher interest to the beginning of the loan term and gradually reduces it.

Nortridge’s Support for Add-On and Rule of 78s

Nortridge allows servicers to configure loans with add-on interest and the Rule of 78s, automating the distribution and calculation so that each payment aligns with the structured interest allocation. This feature is essential for consumer loans where early repayment carries higher interest costs.


Adjusting for Daily and Monthly Interest Rates

Interest accruals can be daily or monthly, depending on loan agreements. Daily accruals compute interest based on the principal balance each day, while monthly accruals apply a monthly interest rate.

Daily Interest Calculation:

Multiply by the days in the period for total interest.

Monthly Interest Calculation:

How Nortridge Supports Daily and Monthly Rates

Nortridge provides flexible configurations for daily and monthly interest accruals, ensuring that interest calculations accurately reflect the loan’s terms. This allows servicers to set schedules tailored to each loan, reducing manual adjustments.


Custom Amortization Schedules

Custom amortization schedules are valuable for loans with unique payment terms, irregular dates, or varying interest rates. Nortridge allows for these complexities by calculating payments based on actual interest year settings, adapting to the unique structure of each loan.

How Nortridge Handles Custom Amortization

NLS’s “Amortize Based on Actual Interest Year” feature projects the loan schedule, adjusting for any discrepancies in the final payment. This automated adjustment ensures that each payment is precise and aligned with the loan’s customized setup, no matter the start date or initial period length.

Example:
For a $10,000 loan with a January 15 origination and a first payment on March 1 at 12% interest, Nortridge calculates the best-fit payment amount by iterating through adjustments. This ensures that the loan will be fully repaid on schedule without manual recalculations.


Tips for Accurate Interest Calculation

For optimal accuracy, servicers should consider these practices:

Verify Calculation Method

When figuring interest on a loan, ensure the calculation method aligns with the loan agreement. Nortridge supports multiple methods, ensuring flexibility.

Adjust for Partial Periods

Loans with irregular periods or mid-period payments may require adjustments, which Nortridge accommodates.

Leverage Automation

Nortridge’s automated calculations reduce errors and maintain consistency, making interest management efficient across portfolios.

Using Accrual and Cash Basis Accounting

Nortridge supports both Accrual Basis Accounting (default) and Cash Basis Accounting.

Accrual Basis

Daily interest accruals post automatically to the general ledger, supporting ongoing revenue recognition.

Cash Basis

Cash Basis requires custom mapping of placeholders, enabling interest revenue to post only upon payment.

Nortridge enables loan servicers to accurately manage interest according to their accounting preferences, supporting both proactive and reactive revenue recognition.


Calculating Interest on a Loan Easily with Nortridge Loan System

Managing diverse interest calculations and amortization schedules can be challenging, but Nortridge Loan System simplifies every step. From handling simple interest loans to configuring custom amortizations, Nortridge empowers loan servicers to calculate interest on a loan with confidence and precision. Ready to enhance your lending operations and offer transparent, efficient loan servicing? Request a free demo with Nortridge today and discover how our robust loan management software can optimize your processes and improve borrower satisfaction.

Webinar: Interest Rate Options in Nortridge Loan System

The following video explores Nortridge Loan System’s interest rate options, from fixed and variable rates to compounding, default, and post-maturity rates. Each setting can be tailored to fit specific loan terms, helping servicers manage diverse borrower needs accurately

Schedule a Demo

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