Trading Margin Calculator

How to calculate trading margin requirements

Regulation T sets initial margin at 50% for marginable stock, so $30,000 of equity buys up to $60,000 of it. For shorts, the regulation requires 150% of the stock's value, which is the sale proceeds plus 50%. Brokers can require more.

After entry, FINRA Rule 4210 sets maintenance at 25% of market value for a long stock. A short stock at $5 or above needs the greater of 30% or $5 a share, and a short stock under $5 needs the greater of 100% or $2.50 a share. This calculator applies those floors to short positions. A margin account also needs at least $2,000 of equity.

Since June 4, 2026, FINRA's intraday margin standard has also applied to positions held during the day, with a phase-in allowed until October 20, 2027. The maintenance percentages themselves did not change.

Long call price = loan ÷ (shares × (1 − maintenance %)). Short call price = (equity + shares × entry) ÷ (shares × (1 + maintenance %)).

Worked example

With $30,000 of equity you buy 120 shares at $500, a $60,000 position with a $30,000 loan. At 25% maintenance, the margin call comes at $30,000 ÷ (120 × 0.75), which is $333.33.

At that price the shares are worth $40,000. Subtract the $30,000 loan and $10,000 of equity remains, which is exactly 25%. A short of 100 shares at $50 with $10,000 of equity reaches 30% maintenance at $115.38.

What the result does not account for

• Your broker's house requirements, which can be higher and can change without much warning, especially on volatile stocks.
• Margin interest, which lowers your equity the longer you hold.
• Other positions in the account, because this treats the position as the whole account.
• Intraday margin deficits, and borrow fees on short positions.

Rules and sources

We checked these rules on November 2, 2026 against Regulation T, 12 CFR 220.12, FINRA Rule 4210 and FINRA Regulatory Notice 26-10.

Frequently asked questions