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RSI (relative strength index), explained

RSI is a quick gauge of whether a stock's recent move has run too far. Here's how to read it without being misled by it.

By Nathan Wickham-Hurd · Founder, Oak Growth · Last reviewed June 2026

What it is

The relative strength index is a momentum indicator that moves between 0 and 100. It measures how fast and how far a stock has moved recently, to gauge whether a run has gone too far in one direction. It's about the price's behaviour, not the company's fundamentals.

How to read it

RSIReading
Above 70Potentially overbought — the rally may be stretched
30 – 70Neutral range
Below 30Potentially oversold — the sell-off may be overdone

How to use it sensibly

RSI is a timing aid, not a buy or sell button. A stock can stay "overbought" for a long time in a strong uptrend, and "oversold" while it keeps falling. It's most useful as a sanity check — flagging when a price move may have run ahead of itself — and best combined with the fundamentals and the trend, never used alone.

Oak Growth shows RSI alongside moving averages so you can read momentum and trend together.

Put this into practice — open the screener →

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