Your inputs

Model a margin trade

Entry price

Price per share when you buy, from $0.0001 through $1,000,000.

Whole shares only, from 1 through 100,000,000.

Advanced assumptions

Initial margin

Share of the position you fund with your own cash. Reg-T default is 50%.

Maintenance margin

Equity floor before a margin call. FINRA minimum is 25%; brokers often require more.

Margin interest rate

Annual rate your broker charges on the borrowed amount, 0% through 100%. Use 0 if none.

Days held

How long the loan is outstanding, from 0 through 3,650 days. Use 0 to skip interest.

Your inputs are calculated locally and are not stored.

Margin call price$66.67

A $10,000.00 position on $5,000.00 of equity is 2.0× leverage — a 33.33% drop to $66.67 triggers a maintenance call, and 30 days of borrowing costs $32.88.

Position value: $10,000.00
Your equity: $5,000.00
Borrowed: $5,000.00
Leverage: 2.00×
Margin interest: $32.88
Drop to margin call: 33.33%

Formula & methodology

How margin trading math works

When you buy on margin, you put up part of the position value as equity — the initial margin — and borrow the rest from your broker. Your equity requirement is the position value times the initial margin percentage, and your leverage is simply one divided by that percentage: at 50% initial margin you control $2 of stock per $1 of equity, or 2× leverage. Leverage cuts both ways — 2× leverage doubles your gains on equity, and it doubles your losses too, so a 10% move in the stock is a 20% move in your account. The margin-call price for a long position is the price at which your equity falls to the maintenance requirement, and margin interest accrues on the borrowed amount at a simple annual rate prorated by days held.

Equity = Position value × Initial margin %
Leverage = 1 ÷ Initial margin %
Margin-call price = Entry × (1 − Initial margin %) ÷ (1 − Maintenance margin %)
Interest = Borrowed × Rate × Days ÷ 365

Position value: Entry price × shares
Initial margin %: Share of the position you fund with cash
Maintenance margin %: Equity floor before a margin call
Borrowed: Position value minus your equity
Rate: Annual margin interest rate
Days: How long the loan is outstanding

Worked example

100 shares at $100 on 50% initial margin

Suppose you buy 100 shares at $100, a $10,000 position, with a 50% initial margin requirement. You put up $5,000 of equity and borrow the remaining $5,000, giving you 2× leverage. With a 25% maintenance margin, the margin-call price is $100 × (1 − 0.50) ÷ (1 − 0.25) = $66.67 — a 33.33% drop from your entry. If your broker charges 8% annual margin interest and you hold for 30 days, the loan costs $5,000 × 8% × 30 ÷ 365 = $32.88.

This is an educational calculation based only on the values you provide. It does not look up live prices or your broker’s actual terms, and it is not investment advice.

Assumptions

What this calculator assumes

Defaults follow Regulation T’s 50% initial margin and FINRA’s 25% maintenance minimum — but brokers set house requirements, which are often higher, especially on volatile stocks.
Margin interest is simple interest on the borrowed amount over the days held, not compounded daily the way most brokers actually charge it.
The account holds one long position with no other collateral, cash, or holdings that could absorb a drawdown.
No commissions, borrow fees, or taxes are modeled — every figure comes from the values you enter.
Money values are rounded to the nearest cent for display.

Common questions

Margin trading FAQ

What actually happens at a margin call?

Your broker demands that you restore your equity to the maintenance requirement — by depositing cash or marginable securities, or by selling positions. If you do not act quickly, the broker can liquidate holdings in your account to cover the shortfall, and it is generally not required to ask you first or let you choose which positions are sold.

Why is my broker’s requirement higher than 25%?

FINRA’s 25% is only the regulatory floor. Brokers set their own house requirements above it — 30% to 40% is common for broad-market stocks, and volatile or concentrated names can carry 40% to 100% requirements, which makes the margin-call price much closer to your entry. Enter your broker’s actual figure in the maintenance margin field to model it.

Is margin interest tax-deductible?

Sometimes. In the US, margin interest can qualify as investment interest expense, which is deductible up to your net investment income if you itemize — with several exceptions and limits. This calculator does not model any tax treatment, so talk to a tax professional about your situation.

Primary sources

Sources and review notes

FINRA — Purchasing on Margin, Risks Involved with Trading in a Margin Account
U.S. Securities and Exchange Commission, Investor.gov — Margin Borrowing
Reg T, 12 CFR §220 — Federal Reserve Board

Methodology last checked Jul 16, 2026. Formula implementation is covered by deterministic unit tests. No financial professional review is claimed yet.