Finance calculator

Free margin calculator

Calculate margin requirements and margin call threshold for leveraged positions — enter account equity, position size, and maintenance margin, updated live, as you type.

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Results are estimates. Consult a professional.

How it's calculated

How the margin calculator works

A margin account allows you to borrow from your broker to purchase more securities than your cash alone would allow. The margin requirement is the percentage of the total position value you must fund with your own equity. FINRA and the Federal Reserve's Regulation T set a 50% initial margin requirement — meaning you can borrow up to half of any new stock purchase. Each broker also sets a maintenance margin (typically 25%) below which your equity must never fall.

The two key calculations are (1) how large a position you can open with your equity, and (2) at what price your broker will issue a margin call — a demand to deposit more funds or sell securities to restore the required equity ratio.

Maximum position size = Account equity ÷ Initial margin requirement

Margin loan = Position size − Account equity

Margin ratio = Account equity ÷ Total position value

Margin call triggered when: Margin ratio < Maintenance margin %

Margin call price = Loan amount ÷ (1 − Maintenance margin %)

Stock drop to trigger margin call = (Position size − Call price) ÷ Position size

FINRA Rule 4210 — Margin Requirements: initial and maintenance margin rules for broker-dealers.

Example

Worked example: $10,000 equity buying $20,000 of stock on margin

Example: $10,000 equity, 50% initial margin, 25% maintenance margin

Casey has $10,000 in a margin account and uses the maximum allowed leverage under Regulation T (50% initial margin) to buy $20,000 worth of stock. The broker lends $10,000 (the margin loan). The broker's maintenance margin is 25%. How far can the stock fall before Casey gets a margin call?

Position value = $20,000 | Loan = $10,000 | Equity = $10,000

Margin call price = $10,000 (loan) ÷ (1 − 0.25) = $13,333

Stock drop trigger = ($20,000 − $13,333) ÷ $20,000 = 33.3%

At margin call: Equity = $13,333 − $10,000 = $3,333

Margin ratio = $3,333 ÷ $13,333 = 25% ✓

33% drop triggers margin call

At 2× leverage with 25% maintenance margin, a one-third decline in the stock price is enough to trigger a margin call. Leverage amplifies both gains and losses — a 33% stock drop wipes out two-thirds of your equity at 2× leverage.

Quick reference

Margin requirements and margin call triggers at various equity levels

The table below shows maximum position size, margin loan, and the price drop that triggers a margin call for different equity amounts and initial margin settings. All examples use 25% maintenance margin.

Equity	Initial Margin	Max Position	Margin Loan	Margin Call Trigger
$5,000	50%	$10,000	$5,000	33% drop
$10,000	50%	$20,000	$10,000	33% drop
$10,000	40%	$25,000	$15,000	20% drop
$25,000	50%	$50,000	$25,000	33% drop
$25,000	33%	$75,000	$50,000	11% drop

Source: FINRA Rule 4210 and Regulation T (12 CFR § 220). Maintenance margin fixed at 25%. Higher initial margin lowers leverage and widens the buffer before a margin call.

Practical tips

Tips for managing a margin account safely

Margin amplifies returns in rising markets but accelerates losses in falling ones. These guidelines help you use it without getting caught in a forced sale at the worst possible time.

Keep a margin buffer above the maintenance threshold — Operating at exactly the minimum is dangerous. A single bad day can trigger a call. Aim to stay at least 10–15 percentage points above the maintenance level, especially in volatile markets.
Know your broker's house requirements — Many brokers impose higher maintenance margins than FINRA's 25% minimum, particularly for small-cap stocks, ETFs with leverage, or concentrated positions. Check the specific maintenance requirement for each security you hold on margin.
Margin calls can be met with cash or securities — but timing is tight — Most brokers give you 2–5 business days to meet a margin call, but in extreme markets they may liquidate positions immediately without notice. Pre-fund your account rather than waiting for a call.
Interest accrues daily on the margin loan — Margin interest rates are typically tied to the broker call rate plus a spread. On a $20,000 loan at 7% annually, you owe about $3.83/day. Long-term margin positions can erode profits significantly.
Stress-test your position before entering — Before buying on margin, calculate the exact percentage drop needed to trigger a margin call. If that threshold seems reachable in normal market conditions for that security, reduce your position size.

Accuracy & limits

Accuracy and limitations

This calculator applies the standard Regulation T (50% initial margin) and FINRA Rule 4210 (25% maintenance margin) formulas. Actual margin requirements vary by broker, security type, account size, and market conditions. Many brokers set higher house maintenance margins (30–40%) for individual stocks, require 100% margin for certain securities, or restrict margin borrowing on specific tickers entirely. The calculator does not model pattern day trader (PDT) rules, portfolio margin accounts, or the daily compounding of margin interest. For precise figures, consult your broker's margin agreement and rate schedule.

Not financial advice — consult a financial professional for your specific situation.

Glossary

Key margin account terms

The minimum percentage of a new position's value that must be funded with your own equity at purchase. Set at 50% by Regulation T for most US stocks.

The minimum equity ratio you must maintain at all times. FINRA Rule 4210 sets the floor at 25%; brokers may require more. Falling below triggers a margin call.

A broker's demand that you deposit additional cash or securities — or sell holdings — to restore your equity ratio above the maintenance margin level. Failure to meet a margin call allows the broker to liquidate positions without your approval.

The amount borrowed from the broker to fund the portion of your position above your equity contribution. Interest accrues daily until the loan is repaid.

A Federal Reserve regulation (12 CFR § 220) that governs the extension of credit by brokers and dealers. Requires investors to fund at least 50% of a new stock purchase with their own cash.

Total position value divided by account equity. At 50% initial margin the leverage is 2:1; you control $2 in stock for every $1 of equity. Higher leverage magnifies both gains and losses.

About

About this margin calculator

This calculator runs entirely in your browser — nothing you enter is sent to any server.

Part of our finance calculators suite — explore all calculators.

Questions

Frequently asked questions about the free margin calculator

A margin calculator is a free online tool that helps you calculate margin loan, buying power, and margin call price. Margin lets you borrow against existing stock holdings. Margin call when equity drops below maintenance %. It runs entirely in your browser with instant results and no sign-up.

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