π³ Margin Interest Calculator
What your broker charges for borrowed money.
Interest for the period
Estimates for planning only, not financial advice.
Margin interest is the daily rent on borrowed investing money: balance x APR / 360 x days. A $25,000 margin balance at 9 percent for 45 days costs $281.25, or $6.25 a day. This calculator prices any balance, rate, and holding period, and shows the daily, monthly, and annualized cost so the drag is visible.
The rate looks modest until it compounds against you. Nine percent certain cost must be cleared by uncertain returns every year the loan runs, which is why margin works for weeks and bleeds for years. Price the interest before judging the trade.
How to Use This Calculator
Enter the margin debit balance, the broker's annual margin rate, and the number of days borrowed. The calculator returns the period interest plus daily and annualized equivalents.
Enter the margin balance you carry. Use the average if it fluctuates.
Enter the broker's margin APR and the days you expect to hold the balance.
Read the interest cost. For the liquidation risk running alongside it, our margin call calculator finds your trigger price.
The Formula
Brokers use a 360-day year by money-market convention, which makes the effective cost slightly higher than the nominal APR suggests. Interest accrues on the daily balance and posts monthly, after which it compounds: the interest itself starts earning interest at the same rate. Over a full year, 9 percent nominal with monthly posting behaves like about 9.38 percent effective.
What Margin Rates Look Like
| Broker type | Typical margin APR | $25k for 45 days |
|---|---|---|
| Full-service wirehouse | 10 to 13% | $312 to $406 |
| Mid-tier online broker | 8 to 10% | $250 to $312 |
| Discount, large balance tier | 5 to 7% | $156 to $219 |
The spread is the story: the same $25,000 for the same 45 days can cost $156 or $406 depending on the broker. Rate shopping is the highest-return phone call in leveraged investing. Rates are tiered by balance and float with the broker's base rate, so recheck yours whenever the Fed moves.
Worked Example
With the defaults: $25,000 balance at 9 percent for 45 days. Daily interest is 25,000 x 0.09 / 360 = $6.25. Over 45 days that is $281.25, which is 1.13 percent of the balance. The monthly equivalent is $187.50, and holding the balance a full year would cost $2,250 in interest alone, before any market movement. A stock bought on this margin must rise more than 9 percent a year just to cover the carry.
Keeping the Cost Down
Borrow the minimum for the minimum time, repay from the next cash inflow rather than letting balances linger, and negotiate: brokers cut rates for active traders who ask. Consider whether futures or options give the same exposure cheaper; for broad index exposure, futures' implied financing near risk-free rates beats retail margin by points.
My rule: annualize every margin decision. A trade held 45 days at 9 percent feels cheap at $281; stated as $2,250 a year it gets the scrutiny it deserves. Interest is certain, returns are not, and the calendar is always running.
Shopping for Cheaper Margin Rates
Margin rates vary enormously: full-service brokers have charged 10 to 13 percent while discount brokers offer under 7, a gap worth thousands yearly on a $50,000 balance. Rates are tiered by balance, so consolidating at one broker can drop you into a cheaper tier, and negotiated rates exist for large accounts if you ask. Some brokers also offer pledged-asset lines or portfolio margin with better terms for buy-and-hold borrowers.
Compare against alternatives before borrowing. Securities-backed lines of credit often undercut margin rates for large balances, and futures provide built-in financing near risk-free rates for index exposure. Whatever the source, compute the annual drag as a percentage of your expected return: paying 8 percent interest to chase 10 percent returns leaves almost nothing for the risk. For the liquidation risk that accompanies the loan, our margin call calculator shows the trigger price.
The Tax Angle on Margin Interest
Margin interest is generally deductible as investment interest expense, but only against investment income, and only if you itemize. Interest used to buy tax-exempt securities is not deductible at all. The deduction is capped at your net investment income for the year, with excess carried forward indefinitely. Keep clear records of what the borrowed money purchased, because mixed-use borrowing muddies the deduction.
Run the after-tax math before borrowing. At a 32 percent marginal rate, 8 percent margin interest costs about 5.44 percent after the deduction, which still exceeds most realistic expected returns once risk is considered. And remember that the deduction only helps if you itemize; with the standard deduction historically high, many borrowers get no benefit. Consult a tax professional for your situation, because the interaction with capital gains timing adds another layer.
Estimates for planning only, not financial advice.Frequently Asked Questions
How is margin interest calculated?
Brokers charge the annual rate on the daily borrowed balance, usually on a 360-day year: interest = balance x APR / 360 x days. A $25,000 balance at 9 percent for 45 days costs 25,000 x 0.09 / 360 x 45 = $281.25. Interest accrues daily and is typically posted monthly.
What are typical margin interest rates?
They vary widely: full-service brokers often charge 9 to 13 percent, while discount brokers with tiered pricing can go as low as 5 to 7 percent on large balances. Rates are usually tiered, falling as the borrowed amount rises, and they float with the broker's base rate, so they move with Fed policy.
Is margin interest tax deductible?
Investment interest is deductible up to net investment income if you itemize, reported on Form 4952. Interest on margin used to buy tax-exempt securities is not deductible. The deduction does not carry the day for most borrowers, but it trims the effective cost for itemizers with investment income.
Why do brokers use a 360-day year?
Convention from money markets, where the 30/360 day-count simplifies interest math. It slightly raises the effective cost versus a 365-day divisor: the same 9 percent nominal costs about 1.4 percent more in real terms. The difference is small per day but real across a year.
Does margin interest compound?
Yes, in effect. Unpaid interest is added to the debit balance, and the next day's interest accrues on the larger balance. Monthly posting makes the compounding visible. Over a full year at 9 percent nominal, the effective rate with monthly compounding is about 9.38 percent.
How can I reduce margin interest costs?
Borrow less, repay quickly, and negotiate or switch brokers: rate shopping can cut the APR by several points. Some brokers offer lower promotional rates. The cheapest margin interest is the interest you never incur by sizing positions to cash.
What is the difference between margin interest and a margin call?
Interest is the ongoing rental cost of borrowed money, charged daily regardless of performance. A margin call is the broker's demand for more collateral when equity falls too low. High interest does not trigger calls, but the combined drag of interest plus falling prices ends leveraged trades.
Are there alternatives to margin loans?
Yes: portfolio lines of credit, futures for leveraged exposure with implied financing near risk-free rates, and LEAPS options for defined-risk exposure. Each has its own cost structure, and futures financing is often far cheaper than retail margin rates for equivalent exposure.
Do short sellers pay margin interest?
Short sellers pay interest on the cash proceeds credited, usually at a rate below the long margin rate, plus stock borrow fees on hard-to-borrow names that can dwarf the interest. The borrow fee, not the margin rate, is the real cost driver in crowded shorts.
When does margin interest make sense?
For short, deliberate, well-collateralized needs: bridging settlement, short-term flexibility, or a high-conviction position held briefly. As a permanent portfolio feature it is a treadmill, since the certain interest cost must be beaten by uncertain extra returns every single year.