Range Base Rate
How often a stock or ETF closed inside a band, closed above its open or the prior close, filled an opening gap or took the prior day’s high, 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.
Switch What to measure to direction, gaps and the prior high and low for the session base rates: how often the ticker closed above its own open and above the prior close, opened above the prior close, traded back to the prior close after opening a set distance away, and traded through the prior session's high or low. Each rate prints with its count, and under 20 sessions it is withheld. They are the baseline a directional call has to beat: a service right on 55% of its calls that the close finishes above the open has added little on a stock that did that on 54% of sessions anyway.
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.
On the same bars, the 578 SPY sessions from 1 July 2024 to 19 October 2026: SPY closed above its own open on 51.6% (298) and above the prior close on 55.3% (319 of 577). It opened above the prior close on 58.9%, and the overnight legs carried most of the gain: holding only from each close to the next open returned +31.0%, and only from each open to its close +7.3%. Of the 161 opens 0.5% or more from the prior close, 47 (29.2%) traded back to it the same session.
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.
The open in these daily bars comes from a consolidated summary, not from the listing exchange's official opening price, and we have not confirmed whether the open, high and low include pre-market trades. One sign of the difference: 16 of SPY's 578 opens on file are fractions of a cent, such as 562.865 on 16 July 2024, and none of its closes is. The tool counts these for every ticker it measures, and every rate built on the open carries the difference; the rates on closes do not.
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.
What are the session base rates?
The share of sessions a ticker closed above its own open and above the prior close, opened above the prior close, traded back to the prior close after opening a set distance away, and traded through the prior session’s high or low, each with its count. Under 20 sessions a rate is withheld. Over the 578 SPY sessions to 19 October 2026, SPY closed above its own open on 51.6%.
Is the open the official opening price?
No. The open in these daily bars comes from a consolidated summary, not the listing exchange’s official opening price. 16 of SPY’s 578 opens on file are fractions of a cent and none of its closes is. The tool counts these for each ticker, and the rates built on the open carry the difference.
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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.
What it cannot tell you
It cannot tell you what the next session will do: every rate describes the window on file, which starts on 1 July 2024, and a different window gives a different rate.