What it costs
Updates live as you typeHow far the position can fall
Green is your room to fall. Red is past the maintenance requirement.
What the loan costs over time
Interest accumulated to date, and how much of it comes from letting interest ride.
Your return, borrowed versus cash
Return on the money you put in, over the holding period, at each possible position return.
Month-by-month accrual
| Period | Days | Opening balance | Interest | Cumulative | Closing balance |
|---|
What these numbers mean
Written against the figures you entered, so these update too.
The maths behind it
daily interest = debit balance × (annual rate ÷ day-count year)
call level = loan balance ÷ (1 − maintenance requirement)
leverage helps when: annual return > effective annual rate
Two conventions make the real cost higher than the quoted rate suggests: most US brokers divide by 360 rather than 365, and any interest you don't pay off joins the debit balance, so next month you pay interest on it.
Interest posts every 30 days in this model, which is how a broker's monthly cycle behaves. The full guide works through each number — how brokers accrue and post interest, why the 360-day year quietly raises your rate, why the call level creeps up the longer you hold, and the four mistakes that cost people the most. Read the margin interest guide.