Max pain
The strike at which the options open at one expiry would be worth the least in total if the stock settled there.
Formula
Max pain = the price P minimizing Σ calls OI × max(0, P − strike) + Σ puts OI × max(0, strike − P)
How to read it
A price level, not a forecast. Some traders watch it into expiration on the theory that hedging pins the stock nearby.
How to use it
One more reference level near expiration, alongside the strikes with the most open interest.
Limitations
Ignores who holds the contracts and why. Open interest is reported once a day, so it can be a day old.
In Kereon
Charts · Option Lens. From the chain's own open interest for the selected expiry, checked across the listed strikes.
Investing · Options. The same calculation, for the company's expiries.
Also called: maximum pain, pin, pinning.