Futures contracts on NSE expire every month. A trader who wants to keep a futures position beyond expiry cannot simply hold it: on expiry day it is settled and closed. Instead, the trader rolls it over: closes the position in the expiring (near) month and opens the same position in the next month. Because thousands of traders do this in the last week of every month, rollover shows up clearly in open interest, and the numbers behind it tell you how much of the month's positioning is being carried forward.
If open interest is new to you, start with what is open interest. Expiry days and contract cycles change from time to time, so check the current monthly expiry day on NSE.
How rolling over works
Suppose a trader holds 2 lots of NIFTY futures long in the current month with NIFTY near 25,000. Three days before expiry, they:
- Sell 2 lots of the current-month future (closing the long).
- Buy 2 lots of the next-month future (opening a new long).
Their market exposure barely changes, but their position now lives in the next month. Most brokers and the exchange offer a calendar spread order that does both legs at once at a quoted price difference, which reduces the risk of the market moving between the two orders.
On the open interest of each contract, the effect is clear: OI in the current month falls, and OI in the next month rises by a similar amount. That is why near-month OI always collapses in expiry week, and why reading build-up from the near month alone misleads at that time (see open interest build-up).
Rollover percentage
Rollover % = (next-month OI + far-month OI) ÷ (current + next + far-month OI) × 100
It is usually measured at the close on expiry day or the day before. A worked example for a large bank stock, in shares of open interest:
| Contract | OI (shares) |
|---|---|
| Current month (expiring) | 1.2 crore |
| Next month | 5.6 crore |
| Far month | 0.2 crore |
| Total | 7.0 crore |
Rollover % = (5.6 + 0.2) ÷ 7.0 = 82.9%. Most of the positions have moved forward. If the stock's average over the last three expiries was 74%, this month's rollover is higher than usual: traders are keener than normal to keep their positions.
Rollover cost
The next-month future usually trades above the current month, because of the cost of carrying a position for another month (interest, minus any expected dividends). That difference is the rollover cost or roll spread:
Rollover cost % = (next-month future − current-month future) ÷ current-month future × 100
For example, with the current-month NIFTY future at 25,060 and the next month at 25,210, the spread is 150 points, or about 0.6%. Traders compare this with the usual cost of carry:
- Rollover cost higher than usual: buyers are willing to pay up to carry longs forward. Usually read as bullish.
- Rollover cost lower than usual, or a discount: shorts are being carried forward, or there is little demand for longs. Usually read as bearish.
- Dividends: if a stock will go ex-dividend in the next month, its next-month future trades lower by roughly the dividend. That is not bearish; it is arithmetic.
What is "usual"? The fair spread for one month is roughly the price times the short-term interest rate for one month, less dividends. With interest rates around 6% to 7% a year, a one-month carry of about 0.5% is typical for NIFTY, but rates change, so compare with the last few expiries rather than a fixed number.
Reading rollover with price
Rollover % says how many positions were carried; it does not say whether they were longs or shorts. Price and rollover cost fill the gap:
- Price up over the month, high rollover, rich rollover cost: longs are being carried forward. The trend has support going into the new series.
- Price down over the month, high rollover, cheap rollover cost: shorts are being carried forward.
- Low rollover: traders are closing rather than carrying, so the next month starts with fewer positions. After a strong trend, low rollover can mean the move has run its course.
A live example: options roll too
Options are not rolled in the same formal way, but traders do close expiring options and open positions in the next series, and open interest moves to the new expiry. Here is NIFTY's open interest on the nearest expiry right now:
Near an expiry, watch how quickly the next series' open interest builds: if traders reopen at similar strikes, the support and resistance levels carry over; if they move to new strikes, the range is shifting. Institutional positioning also changes around rollover. The cash flows of foreign and domestic institutions in the same days are here:
Heavy foreign selling in cash during a rollover week, together with cheap rollover cost on index futures, is a consistent bearish picture; heavy buying with rich rollover cost is the opposite. The participant-wise figures that show how foreign investors' futures positions changed are explained in FII positions in index futures and options.
How traders use rollover data
- Gauging conviction: above-average rollover in a trending stock shows that traders want to stay in the trade.
- Index sentiment: NIFTY and BANKNIFTY rollover % and cost, compared with the last few months, are widely reported in expiry week as a gauge of positioning into the next month.
- Spotting crowded trades: very high rollover with very high OI can mean a crowded position that may unwind sharply if the price turns.
- Timing their own roll: traders who hold futures often roll a few days early, before liquidity in the current month thins out, and compare the spread with the usual cost of carry to avoid overpaying.
Limits and common mistakes
- Comparing across stocks. Every stock has its own normal rollover. Compare a stock with its own last three to six expiries, not with another stock.
- Ignoring lot size or contract changes. When lot sizes or contract specifications change (check NSE for current figures), OI comparisons across months can jump.
- Reading too early. Rollover % rises through expiry week. A figure taken three days before expiry is naturally lower than the final one.
- Forgetting dividends and interest rates. Rollover cost depends on carry, so a change in cost is meaningful only against what carry should be.
- Treating it as a forecast. High rollover shows positions were carried. It does not mean they will make money.
Rollover is the monthly census of the futures market: how many positions survived to the next series, and at what price. It is most useful as a check on whether the month's trend still has committed traders behind it.