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Overdraft (OD) Interest Calculator (2026) — Daily Product Method & ₹ Cost Proof
Whether managing seasonal working capital for an MSME enterprise or smoothing cash flow between salary cycles, an Overdraft (OD) facility—also structured in commercial banking as a Cash Credit (CC) account—is the most flexible liquidity tool in Indian banking. Unlike a conventional term loan where borrowers receive a lump sum and are locked into rigid monthly EMIs, an overdraft facility permits borrowers to withdraw funds up to a pre-sanctioned credit limit and repay at will.
Crucially, interest is charged exclusively on the exact funds utilized and for the precise number of days they remain drawn. If an enterprise secures an OD limit of ₹25,00,000 but utilizes zero funds throughout the billing month, interest liability is exactly ₹0. However, mastering the mathematical mechanics—specifically the Daily Product Method and monthly compounding debits—is vital to prevent hidden financial drag and unbilled penal charges.
Key Takeaways
- The Daily Product Calculation Standard: Overdraft interest is calculated daily on your closing ledger balance using the formula:
(Daily Utilized Balance × Annual Interest Rate) ÷ 365. Withdrawing ₹5,00,000 at 10.50% p.a. for exactly 10 days costs just ₹1,438 in total interest, after which the liability terminates the moment funds are redeposited. - The Overdraft Against Fixed Deposit Arbitrage: Availing an OD against a bank fixed deposit carries an interest rate pegged just 1.00% to 1.50% above the underlying deposit rate (e.g., 8.25% OD rate against a 7.25% FD). Because the pledged FD continues earning 7.25% quarterly compound interest across 100% of the deposit, the net effective borrowing spread is only 1.00% to 1.25%.
- Monthly Compounding Interest Risk: Under Reserve Bank of India (RBI) prudential guidelines, accrued daily interest is billed and debited to the OD account on the final day of each calendar month. If the borrower fails to service this interest from external cash flow, the debited amount increases the utilized principal, triggering monthly compounding interest.
1. The Mathematics of the Daily Product Method
Scheduled commercial banks (SBI, HDFC Bank, ICICI Bank, Axis Bank) compute overdraft liabilities through the standardized Daily Product Formula:
Daily Overdraft (OD) Interest Formula
The Monthly Settlement Summation:
At the end of the billing month (comprising N days), total interest billed to the account is calculated by summing all daily interest accruals:
- Sum of Daily Products: Total Product = Sum of (Daily Utilized Balance × Days Active)
- Monthly Interest Debited: (Total Product × Annual Interest Rate) ÷ 365
2. Interactive Overdraft (OD) Interest Calculator
Simulate daily borrowings, fluctuating balances, and calculate your exact monthly interest charge using the computational model below:
3. Structural Comparison: Overdraft vs. Personal Loan vs. Credit Card
To optimize liquidity costs, examine how an overdraft compares against alternate credit mechanisms:
Interest Calculation Basis
Repayment Flexibility
Unutilized Funds Cost
Interest Rate Range
Collateral Requirement
Preclosure / Foreclosure Fees
Best Application
| Features & Metrics | Bank Overdraft Facility (OD / CC)Pay for Use | Unsecured Personal Term LoanFixed Commitment |
|---|---|---|
| Interest Calculation Basis | Daily utilized balance only | Full disbursed principal balance |
| Repayment Flexibility | Anytime without prepayment penalties | Fixed monthly EMIs over 1 to 5 years |
| Unutilized Funds Cost | ₹0 interest (clean limit) | Interest charged on 100% of borrowed sum |
| Interest Rate Range | 8.25% to 14.50% p.a. | 10.50% to 18.00% p.a. |
| Collateral Requirement | Pledged FDs, Property, or Salary Account | Zero collateral (Clean unsecured) |
| Preclosure / Foreclosure Fees | Strictly ₹0 (Statutory standard) | 2.00% to 5.00% + 18% GST (Fixed loans) |
| Best Application | Short-term cash flow and working capital | Lump sum capital purchases |
4. Worked ₹ Numerical Case Study: 30-Day Overdraft Utilization Cycle
To demonstrate the real-world cost advantage of the Daily Product Method, consider an enterprise holding an approved ₹10,00,000 Overdraft Limit at an interest rate of 10.50% p.a. over a 30-day calendar month:
- Days 1 to 5 (5 Days): Supplier invoice payment draws ₹2,00,000.
- Days 6 to 15 (10 Days): Inventory restocking increases utilization to ₹6,00,000.
- Days 16 to 25 (10 Days): Customer collections reduce utilized balance to ₹3,00,000.
- Days 26 to 30 (5 Days): Major receivables clear the balance completely to ₹0.
Let us audit the exact daily products and final interest debit:
30-Day Overdraft Utilization & Daily Product Ledger (₹)
OD Limit: ₹10,00,000 | Interest Rate: 10.50% p.a. | 30-Day Billing Month
| Billing Period | Days in Tranche | Utilized Balance (₹) | Daily Product (Balance × Days) (₹) | Interest Accrued for Tranche (₹) |
|---|---|---|---|---|
| Days 1 to 5 | 5 Days | ₹2,00,000 | ₹10,00,000 | ₹287.67 |
| Days 6 to 15 | 10 Days | ₹6,00,000 | ₹60,00,000 | ₹1,726.03 |
| Days 16 to 25 | 10 Days | ₹3,00,000 | ₹30,00,000 | ₹863.01 |
| Days 26 to 30 | 5 Days | ₹0 | ₹0 | ₹0.00 |
| Full 30-Day Cycle | 30 Days | Average: ₹3,33,333 | Total Product: ₹1,00,00,000 | Total Interest: ₹2,876.71 |
Financial Analysis of the Case Study:
- The Overdraft Advantage: The enterprise had access to a ₹10,00,000 liquidity buffer throughout the month, yet paid a total of just ₹2,876.71 in interest.
- The Personal Loan Trap: If the firm had taken a conventional ₹10,00,000 personal loan for the same 30-day period, they would have paid interest on the entire ₹10,00,000 for the entire month—incurring ₹8,630 in interest plus a 1.5% processing fee (₹15,000 + GST), costing over ₹26,000 in total outlays.
5. Varieties of Overdraft Facilities in Indian Banking
Lenders structure overdraft facilities under diverse operational categories:
1. Overdraft Against Fixed Deposit (OD-on-FD)
The most cost-effective credit instrument in India. Banks permit drawings up to 90% to 95% of the pledged deposit value. Sanction is typically instant via net banking without income documentation or CIBIL score underwriting.
2. Salary Overdraft (Advance Salary Account)
Extended to salaried corporate employees, allowing drawings up to 2x to 3x net monthly salary. The overdraft is automatically cleared when monthly payroll is credited to the account.
3. Home Loan Overdraft (Smart / MaxGain Facilities)
Facilities like SBI MaxGain or Bank of Baroda Home Loan Advantage link an overdraft current account to your primary mortgage. Surplus liquidity parked in the account immediately reduces the principal on which daily home loan interest is computed, generating massive long-term interest savings.
6. Three Operational Rules to Prevent Cost Traps
- Service Monthly Interest Promptly: Always transfer funds to cover the monthly interest debit before the last day of the month to prevent capitalization into principal and negative compounding.
- Beware of Unutilized Limit Commitments: For corporate accounts with sanctioned limits exceeding ₹50 Lakh, banks may levy a Commitment Charge (0.25% to 0.50% p.a.) on the unutilized portion if average monthly drawing drops below 50% of the limit.
- Never Exceed the Drawing Power (DP): Drawing funds beyond your sanctioned limit triggers punitive penal interest of 2.00% to 3.00% p.a. over the base rate, alongside formal credit bureau default reporting.
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Frequently Asked Questions (FAQs)
How is interest calculated on an overdraft account in India?
Overdraft interest is calculated using the Daily Product Method. The bank computes interest each day on the closing utilized balance at the contractual annual interest rate divided by 365. The sum of these daily interest calculations is debited to the overdraft account on the final business day of each calendar month.
Do I have to pay interest if I do not withdraw money from my overdraft limit?
No. For standard retail overdraft facilities (such as OD against fixed deposits or salary overdrafts), interest is charged strictly on the funds actually drawn. If your utilized balance is zero throughout the month, you pay zero interest. Certain corporate wholesale facilities, however, may levy nominal commitment charges on unutilized balances.
How does an overdraft against a fixed deposit work?
When you take an overdraft against an FD, the bank liens your deposit and sanctions a credit limit of 90% to 95% of the deposit principal. You can withdraw funds as needed, paying interest typically 1.00% to 1.50% above your FD coupon rate solely on the amount utilized. Meanwhile, your underlying fixed deposit continues earning full interest on its entire balance.
What happens if I cannot repay the overdraft principal?
Overdraft facilities do not mandate fixed monthly principal repayments like term loans; you must only ensure that monthly interest debits are serviced and the account stays within sanctioned drawing limits. For secured overdrafts, if you fail to repay or service interest, the bank will liquidate the pledged collateral (such as your fixed deposit) to recover its dues.
Can an overdraft facility affect my CIBIL credit score?
Yes. An overdraft account is reported to credit bureaus as a revolving credit line. Maintaining an excessively high credit utilization ratio (e.g. continually maxing out 90%+ of your limit) or delaying monthly interest payments will negatively impact your CIBIL score. Conversely, disciplined usage and prompt interest servicing builds a strong credit history.
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