About Half on a Double
Half on a Double publishes three price levels for every US stock and ETF with listed options, recomputed after each trading day from the entire options open interest on that ticker:
- Delta neutral – the underlying price at which the summed delta of all open contracts is zero.
- Gamma neutral – the price at which the summed gamma is zero.
- Gamma max – the price at which the summed gamma is largest.
Alongside the levels, the site records total open interest, the split between calls and puts, and the number of contracts, so you can see how positioning has shifted over time. Coverage is roughly 5,600 tickers a day and the history runs back to December 2020. All of it is on the chart, free, with no account.
Why “half on a double”
The name is a risk rule, not a promise. When a position doubles, sell half. The original stake comes back out, the remainder rides for free, and the decisions that follow are made without the pressure of money on the line. Everything the site publishes is meant to serve that kind of disciplined, rational decision-making rather than to generate excitement.
Where the numbers come from
End-of-day options data for every listed US contract is licensed from a commercial vendor. Implied volatility is backed out of each contract’s closing mid price with the Black-Scholes model, the portfolio-level greeks are summed across every open contract, and the levels are found by re-pricing that portfolio at different underlying prices. The methodology page walks through the assumptions, including the ones that are simplifications. Only derived aggregates are published; the underlying contract-level data is not redistributed.
History
The levels were first published in 2021 at options.hardyrekshin.com and moved to halfonadouble.com in 2023. The 2023 blog archive on this site records a period when daily trade ideas were posted; those posts are kept as a historical record and are not maintained.
Who runs it
Half on a Double is a small, independent project with no institutional backing and nothing to sell. Questions, corrections and data problems go through the contact page.
What this site is not
Nothing here is investment advice, a recommendation, or an offer to buy or sell any security. The site is not a registered investment adviser in any jurisdiction. Read the disclaimer before relying on anything published here.