Range Base Rate
How often a stock or ETF closed inside a band around its prior close, measured on every session on file, with the count, the window and the dates.
How it works
Pick a ticker, a band (say ±1%) and how many sessions ahead to look. For every session we hold, the tool takes that day's close, looks at the close that many sessions later, and counts whether it landed inside the band. The share that did is the base rate: what placing the same band every single day, with no judgment about which days, would have earned.
Premium sellers live in this number. An iron condor or credit spread keeps its credit when the price stays inside its strikes, and over most windows it usually does. So a published win rate means little until it sits beside the base rate for the same strikes and the same holding period: the edge, if any, is the gap between them.
Worked example
Over the 577 sessions from 1 July 2024 to 19 October 2026, SPY closed within ±1% of the prior close on 79.0% of next sessions, QQQ on 63.8% and IWM on 61.7%. Five sessions out, SPY stayed within ±2% on 72.8% of tries.
A trading service reported a 76.1% win rate over 92 condor trades on two indexes. The same strike distances, placed on every 2026 session of those indexes, finished inside 63.1% of the time. Measured in the spread a 92-trade record shows by chance, 76.1% is about 2.6 standard errors above 63.1%: unusual, and still a gap of 13 points, not 76.
What it does not tell you
A base rate depends on its window: the one on file starts on 1 July 2024, and a calmer or wilder stretch gives a different rate. Windows longer than one session overlap, so the tool also prints how many of them are independent. It is a measurement of the past, never a forecast, and it says nothing about the size of the wins and losses, which the spread calculator shows.
FAQ
What is a range base rate?
The share of sessions on which a stock closed inside a band around a starting close, measured on every session in the window. It is what placing the same band every day, with no judgment, would have earned.
Why compare a claimed win rate with it?
A credit spread or iron condor wins when the price stays inside its strikes, and most do most of the time. A service that reports a 76% win rate on strikes that finish inside 63% of the time anyway is claiming the 13 points between them, not the 76.
What does "standard errors above the base rate" mean?
How far the claimed rate sits from the base rate, measured in the spread a record of that many trades would show by chance if each trade had only earned the base rate. Around 2 or more is unusual; it does not say why.
Which data does it use?
Split-adjusted daily closes for US stocks and ETFs, every session since 1 July 2024. Indexes such as SPX and RUT are not held; SPY and IWM track them.
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Educational disclaimer
A historical measurement for education only, not financial advice and not a recommendation to buy, sell or trade anything. Daily closes are split-adjusted end-of-day data.