What is Net Interest Income and How to Calculate it?

Published on October 06, 2025 | 3 min read

Net interest income (NII) grew by 4% to ₹651 crore during the quarter under review.

Summary

Net interest income (NII) is the difference between the interest earned on loans and the interest paid on deposits by the bank. It is an important financial metric used to assess the profitability of banks. Net interest income consists of two elements: interest revenue and interest expense. For more, let’s dive into a detailed article.

Key Takeaways

Net interest income is calculated by subtracting interest paid to depositors from interest earned from borrowers.
The net interest margin shows the percentage of average interest-earning assets, indicating how efficiently a bank invests its funds to generate a profit.
A higher NII indicates growth in the loan portfolio, while a lower NII suggests defaults or higher interest expenses.
Investors considering banking stocks should review NII to assess financial health.
Changes in market interest rates affect NIM. Rising rates can boost NIM, while falling rates can compress margins.

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Understanding Net Interest Income

Every bank or financial institution operates with the primary objective of earning interest on loans. Net interest income refers to the difference between the interest earned by banks on loans and the interest paid to their depositors.

When banks provide loans to customers, they charge interest. Similarly, when a customer deposits money into a savings account, banks pay interest to the customer.

Formula:

Net Interest Income = Interest Received (Revenue) - Interest Paid (Expense)

Here:

Interest revenue is calculated as:

Interest Revenue = Effective Interest Rate x Financial Asset.

Interest expense is calculated as:

Interest Expense = Effective Interest Rate x Financial Liability

What is Net Interest Margin?

Net interest margin is the percentage of the difference between the interest earned and interest paid.

Formula:

Net Interest Margin = [ Interest revenue - Interest expense ] / Average earning assets.

How to Calculate Net Interest Income and Net Interest Margin?

The formula for calculating net interest income = Interest received - Interest paid.

Let’s understand this with an example:

You deposited ₹1,00,000 into your bank savings account, which pays an interest at 3% per annum.

The bank decided to lend (giving a loan) 80% of ₹1,00,000, that is ₹80,000, to one of the borrowers at an interest rate of 12% per annum.

Therefore:

Savings account interest paid to depositors = 3% of ₹1,00,000 = ₹3000. Interest received from borrower = 12% of ₹80,000 = ₹9,600.

Net interest income = ₹9600 - ₹3000 = ₹6600.

Now, let’s calculate Net interest margin:

In the above scenario, the value of the average earning asset is ₹80,000.

Therefore, NIM (Net Interest Margin) = NII (Net Interest Income) / Average Earning Asset x 100.

NIM = ₹6600/ ₹80,000 x 100 NIM = 8.25%.

Factors Driving the Net Interest Income

Here are the key factors that drive the net interest income of banks and financial institutions:

Interest Rate

Rising interest rates increase a bank’s profitability by widening its net interest margin. Banks earn more income on interest rate-linked loans compared to the interest paid on deposits.

Hedging Strategies

Banks use interest rate swaps, caps, and floors to manage risk and protect net interest income from fluctuations.

Competition

High competition can force banks to raise deposit interest rates and lower loan rates, leading to a decrease in overall NII, net interest income.

How is Net Interest Income Important for Investors?

Here is how net interest income is important for investors while analysing banking and financial services companies.

Profitability Indicator

Net interest income shows how efficiently a bank generates revenue from its sanctioned loans.

Asset and Liability Management

Strong net interest income demonstrates a bank’s ability to manage interest rate risk and balance asset yields against funding costs.

Asset Quality Indicator

High and growing NII indicates a healthy loan portfolio, whereas declining NII suggests rising defaults or high-cost funding.

Valuation of Stock

Consistent growth in net interest income suggests that the bank is performing well, which leads to a higher stock valuation.

Net interest income remains a valuable financial metric for analysing the profitability of banks and financial institutions. The higher the NII signals a growing portfolio, whereas a low NII indicates defaults or rising interest expenses.

Before investing, it is important to check the bank’s NII to understand its financial health and growth in the loan portfolio, enabling an informed decision.

About Author

Subhasish Mandal

Sub-Editor

Finance professional with strong expertise in stock market and personal finance writing, he excels at breaking down complex financial concepts into simple, actionable insights. Holding a Master’s degree in Commerce, he combines academic depth with practical knowledge of technical analysis and derivatives.

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About Upstox

Upstox is a leading Indian financial services company that offers online trading and investment services in stocks, commodities, currencies, mutual funds, and more. Founded in 2009 and headquartered in Mumbai, Upstox is backed by prominent investors including Ratan Tata, Tiger Global, and Kalaari Capital. It operates under RKSV Securities and is registered with SEBI, NSE, BSE, and other regulatory bodies, ensuring secure and compliant trading experiences.