SENSEX expiry 13 August 2026: what the 77,800 options did in the last 30 minutes
On Thursday 13 August 2026 the SENSEX strike nearest the index at 15:00 was 77,800. The index went from 77,784 at 15:00 to 78,080 at 15:30, up 296 points across the settle walk.
The at-the-money legs, 15:00 to 15:30
| Leg | 15:00 | High | Low | 15:30 | End vs 15:00 | Open interest |
|---|---|---|---|---|---|---|
| 77,800 CE | ₹113 | ₹279 15:30 | ₹61.5 15:23 | ₹279 | 2.5× | 4.0M → 2.7M |
| 77,800 PE | ₹41.5 | ₹41.5 15:00 | ₹0.1 15:30 | ₹0.1 | worthless | 8.5M → 5.6M |
Premium of the strike nearest the index at 15:00, sampled every ten seconds from the NSE option chain. Index values are the chain's own quote. Dotted verticals mark a pin-book flip on Gamma Terrain.
What happened
The 77,800 call was ₹113 at 15:00. It reached ₹279 at 15:30, 2.5× its 15:00 price. It ended at ₹279, 2.5× the 15:00 price. Open interest at the strike went from 4.0 million to 2.7 million, so positions were closed through the window.
The 77,800 put was ₹41.5 at 15:00. It never traded meaningfully above its 15:00 price. Its low was ₹0.1 at 15:30, less than half of where it started the half hour. It ended at ₹0.1, worthless. Open interest at the strike went from 8.5 million to 5.6 million, so positions were closed through the window.
Chain quotes were missing 15:00–15:01, 15:01–15:02, 15:02–15:03, 15:03–15:04, 15:04–15:05, 15:05–15:06, 15:06–15:07, 15:07–15:08, 15:08–15:09, 15:09–15:10, 15:10–15:11, 15:11–15:12, 15:12–15:13, 15:13–15:14, 15:14–15:15, 15:15–15:16, 15:16–15:17, 15:17–15:18, 15:18–15:19, 15:19–15:20, 15:20–15:21, 15:21–15:22, 15:22–15:23, 15:23–15:24, 15:24–15:25, 15:25–15:26, 15:26–15:27, 15:27–15:28, 15:28–15:29, 15:29–15:30: the exchange rate-limited the poll in the endgame, so the chart shows a hole there rather than a line. Highs and lows inside a hole are not known.
For context, across 21 NIFTY and SENSEX expiries measured to 2026-09-08, 15 of 42 at-the-money legs doubled at some point in this window, 26 lost half, and 13 ended at or above their 15:00 price. This page states what the tape did. It is not a recommendation to buy or sell anything.
Gamma Terrain shows the pin, the walls, the book read and every large print, tick by tick, on NIFTY and SENSEX.
The recap is the after-photo. The terrain is the window while it happens.
Read every panel behind these numbers, chapter by chapter.
Trading by the Numbers walks through the quantitative reads behind a modern F&O dashboard — order-flow imbalance, footprints, VWAP bands, OI flow, gamma structure and the expiry endgame — in plain trader-to-trader language.