Margin Interest Calculator
Results are estimates based on the values you enter. Recheck your inputs and assumptions before using the output for decisions.
Estimate margin interest on a borrowed investment balance from annual margin rate and the number of days borrowed.
Margin Interest Calculator
Free online margin interest calculator to estimate the borrowing cost on a margin balance from the borrowed amount, annual margin rate, and number of days borrowed. This calculator is useful for traders, investors, finance students, brokerage account users, and anyone using borrowed funds to buy securities. Margin interest can quietly reduce trading and investing returns, especially when positions are held for longer than expected. That is why it is helpful to translate the annual rate into a daily borrowing cost and then into a total interest charge over the holding period.
This calculator uses three simple inputs. Borrowed amount means the part of the position financed by the broker rather than your own cash. Annual margin interest rate means the yearly rate charged on that borrowed balance. Days borrowed means how long the balance stays outstanding. This calculator uses a 365-day year for the daily estimate. Once those values are entered, the calculator shows margin interest cost, daily interest cost, total repayment amount, and annual interest on the same balance. These outputs make it easier to understand the immediate daily cost of leverage and the full cost of carrying a margin loan over time.
The formula of margin interest
Daily interest cost = Borrowed amount x Annual margin interest rate / 365
Margin interest cost = Daily interest cost x Days borrowed
Total repayment amount = Borrowed amount + Margin interest cost
Annual interest on same balance = Borrowed amount x Annual margin interest rate
Here borrowed amount means the money borrowed from the broker, annual margin interest rate means the yearly borrowing rate expressed as a decimal, daily interest cost means the estimated cost per day on that balance, margin interest cost means the total borrowing cost across the holding period, and total repayment amount means the borrowed balance plus the estimated interest charge.
Solved Example
Example 1: Find the margin interest if the borrowed amount is $10,000, the annual margin rate is 9%, and the balance is borrowed for 30 days.
Solve: Daily interest cost = 10000 x 0.09 / 365 = $2.4658
Margin interest cost = 2.4658 x 30 = $73.97
Total repayment amount = 10000 + 73.97 = $10,073.97
Annual interest on same balance = 10000 x 0.09 = $900
Example 2: Find the result if the borrowed amount is $25,000, the annual margin rate is 11.5%, and the balance is borrowed for 45 days.
Solve: Daily interest cost = 25000 x 0.115 / 365 = $7.8767
Margin interest cost = 7.8767 x 45 = $354.45
Total repayment amount = 25000 + 354.45 = $25,354.45
Annual interest on same balance = 25000 x 0.115 = $2,875
Example 3: Find the result if the borrowed amount is $50,000, the annual margin rate is 8%, and the balance is borrowed for 90 days.
Solve: Daily interest cost = 50000 x 0.08 / 365 = $10.9589
Margin interest cost = 10.9589 x 90 = $986.30
Total repayment amount = 50000 + 986.30 = $50,986.30
Annual interest on same balance = 50000 x 0.08 = $4,000
Table of margin interest calculator
| Borrowed Amount | Annual Rate | Days Borrowed | Margin Interest Cost |
|---|---|---|---|
| $10,000 | 9.00% | 30 | $73.97 |
| $15,000 | 10.00% | 60 | $246.58 |
| $25,000 | 11.50% | 45 | $354.45 |
| $50,000 | 8.00% | 90 | $986.30 |
How to use this margin interest calculator
Enter the borrowed amount in the proper input field. After that, enter the annual margin interest rate and the number of days the balance is borrowed. Then click the calculate button. The calculator will show margin interest cost, daily interest cost, total repayment amount, and annual interest on the same balance in the result box.
This calculator is useful when planning the real cost of leveraged investing or trading. A position may look profitable based on price movement alone, but margin interest can reduce that profit or even turn a small gain into a net loss. Looking at the daily interest cost also helps traders decide whether a short holding period or a longer hold still makes sense after financing cost is included.
When using the result, remember that brokers may use different day-count methods, tiered rates, or changing balances over time. Some may charge based on 360 days instead of 365, and the rate can vary by account size or market conditions. Even so, this calculator gives a strong practical estimate of borrowing cost on a stable margin balance. It is useful for trade planning, leverage review, cost awareness, and investment education.