RSI Explained: What Overbought and Oversold Actually Mean

The Relative Strength Index is one of the most widely used momentum indicators in technical analysis, and one of the most misused. The number printed on a chart tells you about the speed of recent price movement. What it does not tell you is where the price is going, a distinction that matters every time someone says a stock is "overbought" and expects a reversal.

What RSI measures

RSI is a momentum oscillator. It compares the average size of recent up moves with the average size of recent down moves over a set number of periods, and plots the result as a line between 0 and 100 in its own panel under the price chart. A stock that rises day after day pushes the line toward 100, and one that keeps falling pulls it toward 0.

The number of periods is a setting. Wilder's own choice was 14, and 14 is still the default on most charting platforms. A period is one bar of whatever timeframe the chart uses, so 14 means 14 days on a daily chart and 14 hours on an hourly one. Both the period and the timeframe can be changed: a shorter period reacts faster and reaches the extreme levels more often, a longer one is slower. The calculation was published by J. Welles Wilder Jr. in his 1978 book New Concepts in Technical Trading Systems.

• Above 70: Traditionally called overbought. Recent up moves have been large compared with recent down moves.
• Below 30: Traditionally called oversold. Recent down moves have been large compared with recent up moves.
• In a trend: In a bull market RSI tends to move between about 40 and 90, in a bear market between about 10 and 60.

The 70 and 30 levels are traditional conventions, not physical laws, and traders can move them, to 80 and 20 for example. In a strong trend RSI can stay overbought or oversold for an extended time. The label "overbought" describes a data state, not a scheduled event.

How to read RSI in practice

Traders use RSI in three broad ways:

• Level readings: Cross above 70 or below 30 as a marker that momentum has reached an extreme. Used alone, this generates many false signals in trending markets.
• The range in a trend: In a bull market RSI tends to hold between about 40 and 90, with the 40 to 50 zone often acting as support. In a bear market it tends to hold between about 10 and 60, with the 50 to 60 zone often acting as resistance. A reading that leaves its usual range is information about the trend, not only about the level.
• RSI divergence: When price makes a higher high but RSI makes a lower high, momentum is weakening even as the price rises (a bearish divergence). The mirror image is a lower low in price with a higher low in RSI (a bullish divergence). Divergence can come before a reversal, but it does not say when, or whether, one will arrive. For more on how divergence between indicators works as a concept, see the signal divergence explainer.

What RSI does not tell you

RSI measures past velocity. It has no information about earnings releases, macro events, or any fundamentals affecting a company. A stock can print RSI 80 and keep climbing for weeks if the catalyst driving it is large and ongoing. A stock at RSI 25 can keep falling if the reason for selling has not been resolved.

RSI also weights recent periods most. Wilder's smoothing works like an exponential average, so older periods fade rather than drop out. A stock that fell for three months and then rose sharply for two weeks can print a high RSI on the default setting, whatever came before.

For further reading on how RSI is built and used, see the guides from StockCharts ChartSchool, Fidelity and Corporate Finance Institute.

RSI as one input among several

Technical traders usually combine RSI with other tools. It works alongside price structure analysis, volume confirmation, and broader trend context. The EquityBias Bias Score synthesizes momentum signals including RSI-type readings alongside analyst activity, news sentiment, and fundamentals into a single composite. When one dimension disagrees with others, the divergence reading flags the conflict rather than burying it in an average.

You can see today's composite reading for any covered stock in the coverage directory.

EquityBias is a market data research tool. Nothing here is financial advice. RSI levels and readings are descriptive of past price movement, not predictions of future performance.