Margin Interest Calculator
Estimate simple interest on a brokerage margin loan, total financing cost, break-even share price and net return on your cash contribution.
Margin financing analysis
| Holding period | Interest | Total cost | Break-even price | Net P&L |
|---|
Margin interest formula
This calculator uses simple interest for a constant loan balance:
Margin interest = loan principal × annual rate × holding days ÷ day-count basis
Margin loan = purchase cost − cash contribution when you use the cash-contribution method.
Break-even exit price per share = (purchase cost + margin interest + fees) ÷ shares
Net P&L = shares × (exit price − purchase price) − margin interest − fees
Verified examples
| Inputs | Interest | Break-even | Net P&L | Return on cash |
|---|---|---|---|---|
| 100 shares at US$50; US$2,500 cash; 12% for 90 days on a 365-day basis; exit US$55; US$10 fees | US$73.97 | US$50.839726 | US$416.03 | 16.6411% |
| 50 shares at US$80; US$1,500 loan; 10% for 60 days on a 360-day basis; exit US$85; US$5 fees | US$25.00 | US$80.600000 | US$220.00 | 8.8000% |
How to use this margin loan calculator
- Choose whether the loan should be derived from your cash contribution or entered directly.
- Enter shares, purchase price, annual margin rate, holding days and the 360- or 365-day basis shown by your broker.
- Add the current or expected exit price and total trading or other fees assigned to the position.
- Compare the entered period with the fixed holding-period scenarios. Use the same loan balance and annual rate when comparing them.
What the results mean
Daily and 30-day interest show the cost of carrying the entered principal at a constant rate. Break-even includes modeled interest and fees, but not taxes or slippage. Return on initial cash divides net P&L by the cash you supplied, so leverage magnifies both gains and losses.
Broker equity before cost is current market value minus the loan principal. Net equity after modeled cost also subtracts interest and fees. These are position-level estimates, not an account-wide maintenance-margin test.
Limits and assumptions
- The calculation assumes a long stock position, a constant loan balance and one fixed annual rate. It does not compound interest.
- Shares and prices must be above zero and no more than 1,000,000,000. Cash, loan and fees may not exceed 1,000,000,000,000.
- The annual rate must be above 0% and no more than 100%. Holding days must be a whole number from 1 through 36,500.
- Cash contribution or implied cash must be above zero and below purchase cost. The modeled loan therefore must be above zero and below purchase cost.
- Inputs accept a decimal point and up to six decimal places. Scientific notation, thousands separators and decimal commas are not supported.
- Brokers may use tiered rates, daily settled balances, different day-count rules, minimum charges or rate changes. Match your statement or agreement before relying on the estimate.
- Dividends, taxes, short-sale borrow fees, maintenance requirements, margin calls, liquidation, commissions not entered, slippage and changing share quantity are excluded.
This calculator estimates financing cost; it does not determine whether your account meets a broker’s initial or maintenance margin rules. Results are educational, not investment advice.
Frequently asked questions
Is margin interest charged daily?
Many brokers accrue it daily and charge it periodically. The exact posting schedule and balance method depend on the broker. This tool prorates one annual rate over the selected basis.
Should I choose 360 or 365 days?
Use the convention in your broker’s margin disclosure or statement. A 360-day basis produces slightly more interest than a 365-day basis for the same principal, rate and days.
Does this calculate a margin call price?
No. Margin call and liquidation thresholds depend on account equity and maintenance requirements. Use the separate Margin Call Calculator for that task.
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- Trailing Stop Loss Calculator — calculate a dynamic exit trigger.