Leg
Each individual contract inside a multi-part strategy is called a leg — the building block of every spread.
Definition
In options trading, a leg refers to one individual option contract that forms part of a larger, combined position. A simple buy or sell of a single option is technically a one-leg trade. A straddle has two legs — one call and one put at the same strike. An iron condor has four legs: two calls and two puts at different strikes. Each leg has its own strike, expiry, type (call or put), and direction (buy or sell), and together the legs create a payoff profile that none of the individual contracts could achieve alone.
Why it matters
Understanding legs is essential because the risk, margin, and behaviour of a strategy are determined by how the legs interact — not by any single leg in isolation. On NSE, SEBI-mandated SPAN margin calculations give margin offsets when opposing legs hedge each other, which is why a short strangle requires far less margin than two naked short options held separately. Missing a leg — either at entry or during an adjustment — can convert a defined-risk position into an undefined-risk one instantly. For example, if you close only the short call leg of a bull call spread without closing the long call, you are left with a naked long call that now has unlimited potential profit but also orphaned premium cost. Brokers on NSE (Zerodha, Upstox, Angel, etc.) have begun offering basket orders that let you submit all legs simultaneously, reducing the execution risk of entering complex strategies one leg at a time.
How it works
Each leg is defined by four attributes: instrument (e.g., Nifty), option type (call or put), strike price, and expiry. When you combine legs, you add their individual deltas, thetas, vegas, and gammas to arrive at the net Greek exposure of the entire position. For example, a short straddle on BankNifty has near-zero delta (one short call and one short put approximately cancel each other's delta at the money) but high negative theta — it profits as time passes, provided the underlying stays near the short strike. The legs also interact on the payoff diagram: profits from one leg can offset losses from another across different price zones, which is what creates the characteristic tent or trough shapes of spreads and condors.
Example
Suppose you set up a bull call spread on Nifty. Leg 1: buy the 24,000 call for ₹150. Leg 2: sell the 24,300 call for ₹70. The net debit is ₹80 per unit (₹2,000 per lot of 25). Each leg exists independently in your broker's system — if you accidentally close Leg 2 (the short call) without closing Leg 1, you now hold a naked long call. Conversely, if you close Leg 1 without Leg 2, you hold a naked short call with unlimited upside risk. Always treat both legs as a single unit when entering, adjusting, or exiting.
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