Why we aggregate open interest across all expiries

Near-month-only open interest makes every symbol shed its positioning in the same week each month. That's the calendar, not the market.

The open-interest figure on each StockLearn F&O page is the total across every live expiry for that symbol — near month, next month and far month combined. That's a choice, and it has a real cost. This piece explains why we made it and what we do to offset the cost.

Three contracts, one symbol

NSE lists stock futures for three consecutive monthly expiries at any time. Liquidity is heavily concentrated in the near month; the next month carries meaningfully less, and the far month usually very little. All three have their own open interest, and all three appear separately in the bhavcopy.

So "the open interest in RELIANCE" isn't a single number until you decide how to combine three.

The case for aggregating

The alternative — reporting near-month only — sounds cleaner and is what many sources do. It has a serious problem that shows up every month.

In the week before expiry, traders roll positions from the expiring contract into the next one. Near-month open interest collapses toward zero. If you report near-month only, every symbol appears to shed most of its positioning in the same few days, then mysteriously regain it. That's not a positioning change; it's a calendar artifact affecting all ~207 F&O symbols simultaneously.

Aggregating across expiries removes it. A rollover moves open interest from one bucket to another inside the total, leaving the total roughly unchanged — which is the truth of the situation. The positions didn't go anywhere.

What aggregating hides

Two things, and both matter.

The near/far split itself is informative. A symbol with unusually high next-month open interest relative to near-month is in a different situation from one where positioning sits almost entirely in the front contract. The aggregate flattens that distinction.

Calendar spreads become invisible. A trader long the near month and short the next is not directional at all, but contributes to open interest in both. In the aggregate that looks like ordinary participation.

Why we also publish the per-expiry table

Because of the above, every F&O page carries a breakdown showing each live expiry separately alongside the aggregate. The headline number answers "how much positioning is there in this symbol", and the table answers "where is it sitting".

Reading them together is the point. A rising aggregate with the increase concentrated in the far month is a different story from the same rise concentrated in the front contract, and you can only see that in the breakdown.

Rollover percentage does related work

The rollover figure on each page measures what share of positioning has moved into later expiries. It's most meaningful in the days approaching expiry, when a high figure indicates positions are being carried forward rather than closed.

It's worth knowing that rollover percentage is conventionally read as a conviction measure — high rollover meaning traders are committed enough to pay the cost of carrying. That reading is plausible and widely repeated. Whether it actually predicts anything is, as far as we know, untested on Indian data at scale, and it's not a claim we make.

Futures only, no options

One more scope note. Everything above concerns stock futures. Options open interest is a separate and much larger dataset with its own strike and expiry structure, and it isn't in our pipeline at all. When our pages say open interest, they mean futures open interest, aggregated across expiries.

This guide is educational and explains how StockLearn interprets common technical indicators, using illustrative examples. It is not investment advice or a recommendation to buy or sell any security.