Home › Guides › Indicators

RSI explained: why "overbought" doesn't mean "about to drop"

RSI is the wiggly line under the chart with 70 and 30 drawn on it. Most guides say "above 70, sell". It leaves out the part that matters most.

Beginner guide · 7-minute read · Updated 2026-10-21

What RSI measures

RSI stands for Relative Strength Index. J. Welles Wilder introduced it in 1978.

It answers one question: lately, have the up candles been bigger than the down candles?

The answer is a number from 0 to 100.

• High number: the recent ups have been much bigger than the downs.
• Low number: the recent downs have been much bigger than the ups.
• Around 50: ups and downs have been about even.

That's it. It measures how fast and one-sided the recent move has been. It doesn't measure value, and it doesn't know what comes next.

How it's worked out (a simple example)

The default looks back 14 candles.

1. Take the average size of the up moves over those 14 candles. Say it's 1.0.
2. Take the average size of the down moves. Say it's 0.5.
3. Divide up by down: 1.0 ÷ 0.5 = 2. This is called RS.
4. Turn it into a 0–100 number: 100 − (100 ÷ (1 + 2)) = 100 − 33.3 = 66.7.

So the RSI reads about 67. The ups have been twice the size of the downs.

If the down moves were close to zero, RSI would get close to 100. If the up moves were close to zero, it would get close to 0.

(Wilder's version smooths the averages a little each candle. Charting apps do this for you.)

The common settings

• Length: 14. This is the default almost everywhere.
• Lines at 70 and 30. Above 70 is called "overbought". Below 30 is called "oversold".
• Some traders use 80 and 20 to see only the more extreme readings.
• A shorter length (like 7) makes the line jumpier. A longer one (like 21) makes it calmer.

Why "overbought" doesn't mean "about to drop"

Here's the thing.

"Overbought" sounds like "too expensive, it must fall". But RSI only says the recent move has been strong and one-sided.

In a strong uptrend, that's exactly what you'd expect. RSI can sit above 70 for days or weeks while price keeps climbing. Selling every time it crosses 70 means selling into strength, again and again.

The same goes the other way. In a steady downtrend, RSI can stay under 30 for a long time. "Oversold" doesn't mean "cheap" or "about to bounce".

That's why Overbought and oversold readings work best as a heads-up, not a signal on their own.

How traders use RSI

• The 50 line. Some traders read RSI above 50 as "buyers have had the upper hand lately", below 50 as sellers.
• Extremes in a range. In a sideways market, readings near 70 or 30 can line up with the top and bottom of the range. This tends to fail when the range breaks.
• Divergence. Price makes a new high, but RSI makes a lower high. That shows the push is getting weaker. It's a warning, not a timing tool. Divergence can last a long time before anything turns, and sometimes nothing turns.

What RSI can't do

• It can't predict. It's built only from past closes.
• It lags. It reacts to moves that already happened.
• It gives false signals. Lots of 70 and 30 crossings lead nowhere.
• Tuning it to the past doesn't help much. You can always find a length and a pair of lines that "worked" on last year's chart. That's overfitting. It usually stops working on new charts.

Where it fits with our method

We read the chart's turning points first: the last places price turned around.

If price keeps making higher highs and higher lows, the trend is up. A high RSI in that trend isn't a reason to sell. It's just the trend being strong.

What would make us think a trend might change? Price itself. A candle body closing below the last higher low says more than any RSI reading. (Wicks poking through don't count.) See how to identify a trend and breakout vs fakeout.

So RSI gets one job, at most: a second opinion. For example:

• The chart shows a turning point at a level you already marked, and RSI shows divergence there. Two things agree. That's worth a closer look.
• RSI says "overbought", but the chart shows a clean uptrend. The chart wins.

One clean read beats six indicators.

Common mistakes

• Selling just because RSI hit 70. In a trend, that's selling into strength.
• Buying just because RSI hit 30. In a downtrend, it can stay low for a long time.
• Treating divergence as a timer. It says the push is weakening, not when price will turn.
• Changing the length until it fits. 14 vs 11 vs 9, chosen to match last month. That's fitting the past.
• Reading RSI instead of the chart. If you look at the line first, you'll start to ignore what price is doing.

Try it today on TradingView

About 10 minutes. Phone or computer.

1. Open a daily chart with a clear uptrend. Add "Relative Strength Index" from Indicators (default 14, 70/30).
2. Count how many times RSI went above 70 while the trend kept going up.
3. Now find a sideways stretch. Do the 70/30 readings line up with the edges better there?
4. Find one divergence: a higher price high with a lower RSI high. What did price do in the next 10 candles?
5. Write down what you saw in your trading journal. One sentence is enough.

Questions