The layout
An option chain lists every strike price for one underlying and one expiry. Calls (CE) sit on the left, puts (PE) on the right, and the strike runs down the middle. The strike closest to the current price is the at-the-money (ATM) strike.
What each column means
| Column | Meaning |
|---|---|
| OI (open interest) | Contracts still open at that strike. High OI = a level many traders have a stake in. |
| Chg in OI | Contracts added (+) or closed (−) today. Shows where fresh positions are being built. |
| Volume | Contracts traded today. High volume with little OI change means intraday churn. |
| IV | Implied volatility — the volatility the option's price implies. Higher IV = costlier options. |
| LTP | Last traded price (premium) of the option. |
| Bid / Ask | Best price buyers and sellers are quoting. Wide gaps mean poor liquidity. |
In the money vs out of the money
- A call is in the money (ITM) when the strike is below the spot price; a put is ITM when the strike is above it.
- ITM options carry intrinsic value; out-of-the-money (OTM) options are pure time value and decay to zero if they stay OTM.
- BullStocks shades ITM cells so you can see the split at a glance.
Turning OI into levels
Option sellers (writers) are usually better-capitalised than buyers, so traders watch where they write. The strike with the highest put OI often acts as support — writers there profit as long as price stays above it. The strike with the highest call OI acts as resistance.
Track how these shift through the day: if put writing moves up to higher strikes, support is rising; if call writers roll down, the ceiling is dropping.
Expected move from the straddle
Add the ATM call and ATM put premiums. That straddle price is roughly the move the market expects by expiry. NIFTY at 25,000 with a ₹250 straddle implies about ±1% by expiry.
Common mistakes
- Treating OI levels as guarantees — big news can blow through any strike.
- Ignoring liquidity: far OTM strikes can have wide spreads.
- Reading one snapshot: the change in OI over the session tells you more than the absolute level.