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{{Refimprove|date=September 2012}}
'''Williams %R''', or just '''%R''', is a [[technical analysis]] [[oscillator (technical analysis)|oscillator]] showing the current closing price in relation to the high and low of the past N days (for a given N).  It was developed by a publisher and promoter of trading materials, [[Larry R. Williams|Larry Williams]]. Its purpose is to tell whether a  [[stock market|stock]] or [[Commodities#Commodity trade|commodity]] market is trading near the high or the low, or somewhere in between, of its recent trading range.

: <math>\%R = { high_{Ndays} - close_{today} \over high_{Ndays} - low_{Ndays} } \times -100</math> <ref>http://stockcharts.com/school/doku.php?id=chart_school:technical_indicators:williams_r</ref>

The oscillator is on a negative scale, from -100 (lowest) up to 0 (highest), considered unusual since it is the obverse of the more common 0 to 100 scale found in many Technical Analysis oscillators. Although sometimes altered (by simply adding 100), this scale needn't cause any confusion. A value of -100 is the close today at the lowest low of the past N days, and 0 is a close today at the highest high of the past N days.

==Buy-/Sell-Signalling==

Williams used a 10 trading day period and considered values below -80 as oversold and above -20 as overbought.  But they were not to be traded directly, instead his rule to buy an oversold was

* %R reaches -100%.
* Five trading days pass since -100% was last reached
* %R rises above -95% or -85%.

or conversely to sell an overbought condition

* %R reaches 0%.
* Five trading days pass since 0% was last reached
* %R falls below -5% or -15%.

The timeframe can be changed for either more sensitive or smoother results. The more sensitive you make it, though, the more false signals you will get.

==Notes==
Due to the equivalence

: <math>{ (close_{today} - low_{Ndays}) - (close_{today} - high_{Ndays}) = high_{Ndays} - low_{Ndays} }</math>

the %R indicator is arithmetically exactly equivalent to the %K [[stochastic oscillator]], mirrored at the 0%-line, when using the same time interval.

{{technical analysis}}

==References==

{{Reflist}}

[[Category:Technical indicators]]