The Most Ignored Column in the Option Chain
When traders open the NSE option chain, most of them look at one thing: LTP (Last Traded Price). They scan for options that look affordable. They buy.
What they scroll past: OI and Chng in OI — the two columns that tell you where large institutional positions have been built, and where they are being added right now.
This data is free. It is updated every 3 minutes during market hours. And it is one of the few genuine edges available to retail traders who know how to read it.
Open Interest (OI) = total outstanding contracts at a strike that have NOT been closed. Every new position opened increases OI. Every position closed decreases it. Unlike volume (which counts every trade including closes), OI measures active commitment.
The Four OI Combinations
Every price and OI combination tells a different story:
| Price Movement | OI Change | Signal | Meaning |
|---|---|---|---|
| Price UP | OI UP | Bullish | New longs being added — strong uptrend |
| Price DOWN | OI UP | Bearish | New shorts being added — strong downtrend |
| Price UP | OI DOWN | Short covering | Bears exiting — weak/unsustained rally |
| Price DOWN | OI DOWN | Long unwinding | Bulls exiting — controlled pullback, not panic |
Long build-up (Price UP + OI UP) is the strongest bullish signal. Real buyers are entering.
Short build-up (Price DOWN + OI UP) is the strongest bearish signal. Real sellers are entering.
Short covering (Price UP + OI DOWN) = bears closing positions, not necessarily new bulls entering. Rally may not sustain.
OI in Options: Finding Support and Resistance
For options, massive OI concentration at specific strikes creates invisible walls in the market.
High Call OI at a strike = Resistance. The traders who sold those calls (option writers) collected premium expecting NIFTY to stay below that strike. If NIFTY approaches their sold strike, they'll aggressively SELL futures to hedge their position — which pushes NIFTY back down.
High Put OI at a strike = Support. Put writers sold puts expecting NIFTY to stay above. If NIFTY falls toward their sold puts, they'll BUY futures to hedge — which provides a floor.
This is why NIFTY often "gravitates" toward the maximum pain level (the strike where both call and put buyers lose the most) near expiry.
How to Use OI Data in Your Trading
Step 1: Morning routine (before 9:15 AM)
Check NSE option chain and identify:
- Strike with maximum Call OI (resistance for the day)
- Strike with maximum Put OI (support for the day)
- Total PCR (Put-Call Ratio) for sentiment
Step 2: Watch for OI changes intraday
The Chng in OI column is crucial. A strike that had 20 lakh OI yesterday but shows +8 lakh new OI today is being heavily targeted.
If 22,500 CE shows massive new OI building while NIFTY approaches 22,500, it signals writers are defending that level aggressively.
Step 3: OI unwinding near expiry
As expiry approaches (Wednesday/Thursday), watch for OI unwinding at support/resistance strikes. When put writers start covering (OI decreasing at put strikes), that support level is weakening — potential breakdown.
Practical Example: Reading OI for a Trade
Scenario: It's Monday. NIFTY is at 22,300.
Option chain shows:
- 22,500 CE: OI = 65 lakh (massive call writing at 22,500)
- 22,000 PE: OI = 58 lakh (massive put writing at 22,000)
- PCR = 1.1 (slightly bearish tilt but neutral range)
Interpretation: NIFTY is likely to stay between 22,000 and 22,500 this week. The range is defined by option writers.
Possible trades based on this:
- 1Range trade: Sell 22,500 CE + Sell 22,000 PE (straddle/strangle). Profit if NIFTY stays in range.
- 2Breakout trade: Buy 22,550 CE if you believe 22,500 resistance breaks. Entry only after sustained price above 22,500 with OI at 22,500 CE starting to unwind.
- 3Avoid: Buying 22,300 CE hoping for unlimited upside — the 22,500 wall is very strong.
Max Pain Theory
Max Pain = the strike price at which option buyers collectively lose the most money at expiry. Mathematically, this is where option sellers (who are often institutions and market makers) profit maximally.
Research shows NIFTY closes near max pain level in roughly 60-65% of weekly expiries. It's not guaranteed, but it's a meaningful probability-weighted anchor.
Calculate max pain on any options calculator. If max pain is 22,200 and NIFTY is at 22,400 with 2 days to expiry, there's gravitational pull toward 22,200.
Common Mistakes in OI Analysis
Mistake 1: Looking at OI in isolation without price movement. Always check the OI + price combination.
Mistake 2: Expecting OI levels to hold perfectly. Institutional orders can overwhelm option writers when big macro events hit.
Mistake 3: Using yesterday's OI without checking today's changes. Fresh OI build-up is more relevant than historical positioning.
Build this habit on PaperPe: every morning before your paper trade session, identify the max Call OI and max Put OI strikes. Write them down. Then watch during the session how price behaves when it approaches those levels. Over 2–3 weeks, you will develop an intuition for when OI walls hold and when they break — an intuition that is genuinely hard to build any other way.