Williams %R Scalp strategy: rules and backtest

Williams %R Scalp catches short reversals out of the overbought and oversold zones on the Williams %R indicator.

How the signal works

Williams %R is the same calculation of where the close sits within the range as the stochastic, but on an inverted scale from −100 to 0. The strategy enters when %R exits the zones below −80 (oversold) and above −20 (overbought), aiming for a return to the midpoint.

The indicator is very sharp — the original formula has no smoothing — so there are many signals and even more noise. In a range this gives frequent entry points; in a trend a stream of premature counter-trend signals.

Verification on real data

This strategy’s rule is run on real quotes with no parameter fitting to history. The rule tested was “Williams %R: reversion from overbought territory”:

• Long as %R exits the zone below −80 to the upside (oversold).
• Short as it exits the zone above −20 to the downside (overbought).
• Exit when %R returns to −50.

Pros and cons

Pitfalls

The main confusion is the inverted scale: the overbought zone sits at the top of the chart, near zero, and reading −20 as oversold is a common mistake. The second trap is trading raw %R without smoothing on a calm instrument, where it touches the extremes almost every bar and breeds random signals.

Who it suits

For active traders of ranging instruments who accept a high noise level in exchange for frequent signals. In a trend the approach must be switched off.

Frequently asked questions