Margin Trading Calculator
Calculates how much equity you must put up and how much margin interest you'll owe when buying stocks on leverage. Use it before entering a leveraged position to understand your true cost and risk exposure.
About this calculator
Margin trading lets you borrow from your broker to buy more stock than your cash alone would allow. The initial margin requirement is the minimum percentage of the position's value you must fund yourself — set by regulation (Regulation T in the U.S.) at 50% for most stocks, though brokers may require more. The total cost of a margin position combines your equity contribution and the interest charged on the borrowed amount. The formula used here is: Total Cost = (stockValue × marginRequirement) + (stockValue × (1 − marginRequirement) × (marginInterestRate / 100) × (holdingPeriod / 365)). The first term is your equity (the margin you post), and the second term is the annualised interest on the borrowed portion prorated for your holding period. Knowing this figure upfront helps you calculate the minimum return required to break even.
How to use
You want to buy $20,000 worth of stock. The initial margin requirement is 0.50 (50%), the margin interest rate is 8% per year, and you plan to hold for 30 days. Equity required: $20,000 × 0.50 = $10,000. Borrowed amount: $20,000 × (1 − 0.50) = $10,000. Interest cost: $10,000 × (8 / 100) × (30 / 365) = $10,000 × 0.08 × 0.0822 = $65.75. Total cost = $10,000 + $65.75 = $10,065.75. This means your stock position must return at least 0.33% ($65.75 / $20,000) within 30 days just to cover borrowing costs.
Frequently asked questions
What is the difference between initial margin and maintenance margin in trading?
Initial margin is the percentage of the purchase price you must deposit when first opening a leveraged position. Maintenance margin is the minimum equity you must maintain as a percentage of the position's current market value after the trade is open. In the U.S., FINRA sets the maintenance margin minimum at 25%, though many brokers require 30–40%. If your equity falls below the maintenance level due to price declines, your broker issues a margin call requiring you to deposit additional funds or sell holdings to restore the required balance.
How is margin interest calculated and when is it charged?
Margin interest accrues daily on the outstanding loan balance and is typically charged to your account monthly. Brokers calculate it as: Daily Interest = Loan Balance × (Annual Rate / 365). The annual margin rate varies by broker and by loan size — larger balances often receive lower rates through tiered pricing. Interest is charged even on weekends and holidays. Unlike commissions, margin interest is a continuous ongoing cost, which means the longer you hold a leveraged position, the more it erodes your net return.
When does a margin call occur and how should investors respond?
A margin call is triggered when your account equity drops below the broker's maintenance margin threshold, usually due to a decline in the value of your leveraged holdings. The broker will notify you to deposit additional cash or marginable securities, or to sell positions to bring equity back above the required level. If you fail to respond promptly, the broker has the right to liquidate positions without your consent, potentially at unfavorable prices. The best response is to act immediately — either by depositing funds or voluntarily reducing the position before forced liquidation occurs.