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 is licensed from a commercial vendor. The site publishes derived positioning levels and aggregate observations, with dates and historical context. The methodology page explains their scope, interpretation and limitations. The calculation implementation and calibration procedures are proprietary; the underlying contract-level data is not redistributed.
History
The levels were first published in 2021 and have been at halfonadouble.com since 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.
Editorial standards
Half on a Double is the publisher of this site’s learning guides and research. The site does not publish individual author or editor profiles. Publisher attribution identifies responsibility for the content; it does not imply professional credentials or an independent review.
- Sources: learning guides link to the exchanges, clearing organizations and other primary references used for options definitions. Synthetic examples are labelled so they cannot be mistaken for a real options chain.
- Observations and models: outstanding contracts and dated market observations are distinguished from model-derived levels. The site’s gamma-exposure convention does not reveal actual dealer holdings, and positioning levels are not price forecasts. See the methodology and limitations.
- Timing: ticker data is updated after the trading day. Use the data-through date shown on a page, rather than the date you visit it. Learning guides are updated when their explanations or sources change; a new market-data date does not mean a guide has been reviewed. Archived posts remain historical records.
- Research: original studies must describe the eligible observations, comparison baselines, missing data and uncertainty. A hypothesis is not a finding, and an inconclusive or negative result must be reported honestly.
- Corrections: send the page URL, the passage or value in question, and supporting evidence through the contact page. Confirmed material corrections should explain what changed on the affected 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.