Price, lot size and margin percentage give the contract value, margin required, effective leverage — and how small a move threatens your margin.
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Index futures margins (SPAN + exposure) run around 10–12% of contract value; volatile stock futures can demand 20–40%. The margin buys you exposure to the full contract value — that's the leverage, and it's why the calculator translates small percentage moves into large fractions of your margin.
A useful discipline: know the "half margin" move before entering. If a 4% move wipes half your deposit and the stock regularly swings 3% a day, the position size — not the market — is the problem. Exchanges revise margins with volatility, so treat the % here as an estimate and your broker's basket calculator as final.
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Start Free — No Credit Card →Every broker publishes a margin calculator (Zerodha, Upstox, Dhan all have one) using live SPAN files from the exchange. The 10–12% default here matches index futures in normal volatility; single stocks vary widely.
Daily mark-to-market losses debit your account; if the balance drops below maintenance requirements you get a margin call, and brokers can square off positions without asking. Peak-margin rules in India also require the full margin upfront intraday.
Leverage amplifies both directions — the danger isn't the number itself but position size relative to your stop. One lot with a disciplined stop can be safer than 'low-leverage' cash positions traded without one. Size from risk, not from available margin.