Stock margin call calculator
How to Calculate Maintenance Margin | Sapling.com To do this, subtract the margin requirement from 1 and multiply by the market (purchase) price. Suppose you buy stock at $40 per share with a 60 percent margin requirement. The amount you borrow is equal to $40 x (1 – 0.60), or $16 per share. Step. Calculate the maximum percentage of borrowed money allowed by the maintenance margin.