Margin Interest Calculator
Find out exactly how much your broker charges in margin interest. Enter the loan amount, the annual margin rate and the number of days you plan to hold — see daily, monthly and total interest cost.
%
days
Total margin interest owed for the number of days held
- 1
Daily rate (annual ÷ 360)
8.5% ÷ 360 = 0.000236US brokers use a 360-day year for margin interest. - 2
Daily interest
10,000 × 0.000236 = 2.3611 - 3
Interest for holding period
2.3611 × 30 days = 70.83
How does this calculator work?
Margin interest = Loan × (Annual Rate ÷ 360) × Days held. US brokers use a 360-day year to compute a daily rate. Enter the loan amount, your broker's annual rate and the holding period to see daily, monthly and total interest costs.
Formula
How this is calculated
Broker margin loans are typically priced as a daily rate derived from the annual rate using a 360-day year — the standard market convention for US margin accounts. The formula is: Interest = Loan Amount × (Annual Rate ÷ 360) × Days Held. This makes the cost directly proportional to how long you hold the position: a loan held for a week is far cheaper than one held for a year.
The calculator computes the daily interest charge, the total interest for the specified holding period, and the equivalent monthly and annual amounts for easy comparison. Most US brokers debit margin interest monthly or at the close of a position.
Note: the 360-day convention is standard in the US; some international brokers use 365 days, which lowers the daily rate slightly. Margin rates also vary by loan balance — larger balances typically attract lower tiered rates. This calculator applies a flat annual rate and does not model rate tiers, rate changes over time, or compounding of unpaid interest. Always check your broker's current rate schedule, as margin rates move with benchmark rates such as the Federal Funds rate.
Frequently asked questions
The 360-day bank discount convention is traditional in US money markets and was adopted by most US brokers for margin lending. It makes each day's interest charge slightly higher than a 365-day calculation would — a small but real difference on large balances held for extended periods.
Most US brokers calculate margin interest daily and debit it to your account monthly on a set settlement date. Some brokers charge it when you close a leveraged position. Check your broker's account agreement for the exact schedule.
In many jurisdictions margin interest on investments is deductible against investment income (not against capital gains or ordinary income). Tax rules vary by country and individual circumstance — consult a tax professional for advice specific to your situation.
TG we-Calculate Editorial Team. (2026). Margin Interest Calculator [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/margin-interest-calculator
TG we-Calculate Editorial Team. "Margin Interest Calculator." TG we-Calculate. 2026. https://we-calculate.com/calculator/margin-interest-calculator.
TG we-Calculate Editorial Team, "Margin Interest Calculator," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/margin-interest-calculator
@misc{wecalculate_margin_interest_calculator, title = {Margin Interest Calculator}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/margin-interest-calculator}}, year = {2026}, note = {TG we-Calculate} }
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