Margin Requirement Calculator (Reg T + Maintenance)
Margin requirement calculator. Reg T initial margin (50%), FINRA maintenance margin (25-30%), buying power, and margin-call trigger price. For long and short stock positions.
Margin Requirement Calculator
How to use the margin requirement calculator
Choose long or short
Long: buying stock with margin. Initial margin 50% per Reg T means you pay 50% cash and the broker lends 50%. Short: borrowing stock to sell. Initial margin still 50% — you must deposit 50% of the short position value to cover the borrowed stock's rise risk.
Enter stock price + shares
Current market price and the number of shares you're trading. Position value = price × shares. For Reg T initial margin: position value × 50% is the cash you need. Note that FINRA's old pattern-day-trader rule (the $25,000 minimum) is being replaced by intraday-margin standards under Regulatory Notice 26-10, effective 4 June 2026 with a phase-in to October 2027.
Adjust margin % if needed
Default: Reg T 50% initial / 25% maintenance for long. Brokers can impose higher requirements (called "house margin") for volatile, low-priced or thinly traded stocks. FINRA itself sets a higher floor for short positions: 30% of market value or $5 a share, whichever is greater, for stocks at $5 or more, and $2.50 a share or 100% for stocks under $5. Check your broker's margin requirement screen for the actual %.
Enter cash available
Used to compute buying power (2× cash at 50% initial) and max shares purchasable. Cash buying power = cash / (initial margin %). Don't deploy all buying power — leaving 30-50% unused gives you margin to absorb adverse moves before getting margin-called.
Read margin call price
Critical number. For long positions: the price the stock can fall to before your equity drops below maintenance %. For shorts: the price the stock can rise to. Beyond it, the broker will demand additional equity within whatever period its margin agreement allows — or liquidate the position, which the agreement usually permits without notice. The "cushion %" shows how much of a move you can absorb.
Margin — how brokers lend you money to amplify trades
Margin in stock trading is essentially a loan from your broker, secured by the securities in your account. Regulation T — the Federal Reserve Board rule issued under the Securities Exchange Act of 1934, after the 1929 crash exposed the dangers of leverage — requires initial margin of 50% of the current market value of a margin equity security (12 CFR 220.12). Translation: with $10K of your own cash, you can control $20K of stocks. FINRA Rule 4210(c) sets maintenance margin (the floor you must maintain) at 25% of market value for long positions and, for short positions, 30% or $5 a share, whichever is greater, on stocks at $5 or more. Brokers often impose stricter "house" requirements on volatile or low-priced stocks. The calculator above shows you the exact margin needed, the loan amount you'll carry, and — most importantly — the margin-call trigger price.
Why margin matters even if you don't use it
Every retail brokerage account is technically a "margin account" by default. Even if you never intend to borrow, understanding margin matters because: (1) Cash sweep — uninvested cash may be lent out by your broker. (2) Settlement timing — US equities settle T+1 (since May 2024), and buying with unsettled proceeds in a cash account can trigger a free-riding violation. (3) Intraday margin — FINRA's pattern-day-trader rule ($25,000 minimum equity, four day-trades in five days) is being replaced by intraday-margin standards under Regulatory Notice 26-10, effective 4 June 2026 with a phase-in to 20 October 2027; check which regime your broker applies. (4) Margin call risk — even cash accounts can have surprises (option assignment, settled cash held back). Every retail trader should understand the calculator above before clicking "buy".
The 1929 crash was largely a margin crash — leveraged investors couldn't meet margin calls, banks called loans, cascade liquidations followed. Reg T (1934) cut maximum leverage in half. Most brokers still cap retail leverage at 2:1 today.
Margin costs — the silent return killer
Margin loans are NOT free. Brokers charge interest on the borrowed portion at a rate they publish, usually a spread over a benchmark rate that falls as the loan grows; the range between brokers is wide, so check the schedule before you borrow. The note beneath the result assumes 10% a year purely for illustration. Margin interest is a real drag on returns. Borrowing $50K at 10% costs $5K per year — the position must outperform by 10% just to cover the interest before any leverage benefit. For long-term investors, margin is rarely worth the cost.
Outside the US
The 50% / 25% / 30% figures above are US rules. Every other market sets its own initial and maintenance margins through its exchange, clearing house and broker agreements, and contracts-for-difference platforms apply different (usually much higher) leverage under their own regulators. The calculator's inputs are editable, so enter the initial and maintenance percentages your broker actually applies and the margin-call arithmetic is the same.
Reg T lends you half; FINRA calls the loan when equity falls to a quarter
Regulation T (12 CFR 220.12): initial margin is 50% of a margin equity security's market value, and 150% for a short sale (100% proceeds plus 50%).
FINRA Rule 4210(c): maintenance margin is 25% of market value for long stock; for short stock it is the greater of 30% or $5 a share ($2.50 a share or 100% below $5).
House margin: brokers can require MORE than Reg T (volatile stocks, low-priced stocks, recent IPOs).
Margin call: the broker demands more equity within the period its margin agreement allows, or liquidates. Forced liquidation often happens at the worst time.
Buying power = cash / initial margin %. $10K cash → $20K buying power at Reg T 50%.
FINRA's pattern-day-trader rule ($25,000 minimum, four day trades in five days) is being replaced by intraday-margin standards — Regulatory Notice 26-10, effective 4 June 2026, phase-in to October 2027.
Margin interest is set by each broker as a spread over a benchmark rate and published on its site — the 10% used in the note above is an illustration, not a quote.
Short selling requires margin. Even cash accounts can't short — you need a margin account.
Portfolio margin (FINRA Rule 4210(g)) sets requirements from portfolio-level stress tests instead of fixed percentages — usually far lower for hedged positions, subject to minimum-equity and approval requirements.
Buying power on Reg T is 2× equity for positions held overnight. Intraday leverage is governed by your broker's margin policy under FINRA's new intraday-margin standards.
Frequently asked questions
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Three options. (1) Deposit cash or securities within the period your margin agreement allows to restore minimum equity. (2) Sell positions to reduce your loan, restoring the maintenance ratio. (3) Do nothing — your broker will liquidate positions at THEIR discretion, often at adverse prices, often without warning. Most margin agreements let the broker do this without prior notice. Don't get into a margin call situation — keep the cushion comfortable.
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Three reasons. (1) Risk-based pricing — retail margin loans have higher default risk than mortgages because the collateral (stocks) can drop 30%+ overnight. (2) Operational cost — brokers manage daily mark-to-market, margin calls, and forced liquidations. (3) Profit centre — margin lending is a significant revenue line for brokers, and the spread over their own funding cost varies widely from one broker to the next. Compare published margin-rate schedules before choosing where to borrow.
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For options strategies + hedged portfolios: very much yes. Portfolio margin (PM) calculates margin based on the entire portfolio's risk under stress scenarios (typically ±15% stock moves with parallel IV moves). A hedged position that requires the full spread width under strategy-based margin can require far less under PM. It is subject to FINRA Rule 4210(g) minimum-equity requirements and to broker approval, and brokers commonly set their own higher minimums. For simple long-stock accounts PM offers little benefit; for hedged, options-heavy accounts it can free up a large share of buying power.
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Yes. Brokers can raise house margin requirements at any time — typically for newly volatile names, pre-earnings, or in response to corporate events. In January 2021 several brokers raised house margin on the most volatile meme stocks to 100%, removing leverage overnight. Brokers generally need not give advance notice — check your account regularly during stress periods. For more stable accounts (large diversified equities, blue-chip ETFs), margin requirements rarely change.
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Yes — three reasons. (1) Higher maintenance margin (30% vs 25% long). (2) Borrow fees for hard-to-borrow stocks (HTB list). Heavily-shorted stocks can carry very high annualised borrow fees. (3) Dividends — the short seller must pay any dividends the underlying pays out, reducing returns. Add it up: shorting can cost materially more per year than going long the same dollar amount. This is why successful short sellers tend to focus on either short-term gambles (binary catalysts) or fundamentally broken structural shorts (frauds, dying businesses).
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Regulation T is a Federal Reserve Board rule (12 CFR Part 220) created by the Securities Exchange Act of 1934. It governs the extension of credit by brokers and dealers for securities transactions. The headline rule: initial margin on US equities is 50% of purchase value. Reg T also covers cash account settlement rules, free-riding, and various securities-lending mechanics. The 50% number has been unchanged since 1974 — a deliberately conservative cap that limits systemic risk in retail markets.
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No — this is for STOCK margin only. Options margin is more complex: Long options require 100% cash (no margin). Cash-secured puts require 100% of the strike × 100 in cash. Naked short options are margined under FINRA Rule 4210(f)(2) — broadly, the premium plus 20% of the underlying value, less any out-of-the-money amount, subject to a minimum. Defined-risk spreads are margined at the difference between the strikes. For options margin, use your broker's position-specific margin calculator. Our iron condor calculator (RT-FIN-235) shows the approximate Reg T margin for a 4-leg iron condor.
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Because this is the single most important number for any leveraged position. The math: for a long position, margin call triggers when equity / market value drops below maintenance %. As the stock falls, your loan stays constant (you owe what you borrowed) but the collateral shrinks, so the equity ratio collapses. Knowing this trigger price BEFORE you open the position is the difference between informed risk-taking and getting blown out. Set a stop-loss above the margin call price to avoid forced liquidation — manage your position before the broker has to.
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No. Position type, price, shares, cash — every input stays in your browser. Margin computations run entirely client-side. Open DevTools → Network when you click Calculate and you'll see zero outbound requests.
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Federal Reserve Regulation T — 12 CFR Part 220, the source document. FINRA Rule 4210 — maintenance margin requirements. SEC Investor Bulletin on margin (sec.gov/investor/pubs/margin.htm) — plain-English consumer guide. FINRA Regulatory Notice 26-10 — the 2026 replacement of the pattern-day-trader rule with intraday-margin standards. Your own broker's margin disclosure statement is the binding document for house requirements and interest rates.
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Method & sources
How it computes
Initial margin = position value × initial % (default 50%, Regulation T); loan = position value − initial margin; buying power = cash ÷ initial %; long margin-call price = loan ÷ shares ÷ (1 − maintenance %); short margin-call price = (initial margin + short proceeds) ÷ shares ÷ (1 + maintenance %); cushion = distance from the current price to the call price. Defaults: maintenance 25% long / 30% short (FINRA Rule 4210(c)); the interest note assumes a 10% margin rate for illustration.
What this tool implements
- Regulation T, 12 CFR 220.12: initial margin 50% of a margin equity security's market value (150% for a short sale = 100% proceeds + 50%)
- FINRA Rule 4210(c): maintenance 25% of market value for long securities; for short securities the greater of 30% or US$5/share at ≥ US$5, and US$2.50/share or 100% below US$5 — the calculator's flat 30% assumes a stock priced at US$5 or more
- Stock positions only; options and portfolio margin are out of scope (stated on page)
- Pattern-day-trader references updated to FINRA Regulatory Notice 26-10 (intraday-margin standards effective 4 Jun 2026, phase-in to 20 Oct 2027)
Sources
- Board of Governors of the Federal Reserve System. Regulation T, 12 CFR §220.12 Supplement: margin requirements. https://www.law.cornell.edu/cfr/text/12/220.12
- FINRA Rule 4210, Margin Requirements — paragraph (c) maintenance margin. https://www.finra.org/rules-guidance/rulebooks/finra-rules/4210
- FINRA Regulatory Notice 26-10, Intraday margin standards replacing the day-trading margin requirements (effective 4 June 2026). https://www.finra.org/rules-guidance/notices/26-10
What can make this go out of date
- FINRA Rule 4210 amendments (Notice 26-10 phase-in through 20 Oct 2027)
- Broker house margin and margin interest rates (per broker, not modelled)
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