# RSI (Relative Strength Index) > RSI is Wilder's relative strength index, a momentum oscillator scaled 0 to 100 that measures how one-sided recent sessions have been by comparing the average size of up-closes to down-closes. Canonical: https://patternsradar.com/learn/rsi RSI splits the last fourteen sessions into gains and losses, smooths each with Wilder's own moving average, and expresses the ratio on a 0–100 scale. A reading of 70 means recent up-days have overwhelmed down-days; 30 means the reverse. Because the smoothing carries long memory, RSI moves deliberately — one big session shifts it, but it takes a run of one-sided sessions to pin it at an extreme. The textbook levels are 70 overbought and 30 oversold, but on daily NSE bars the more useful readings are contextual. In a genuine uptrend RSI rarely touches 30 at all — pullbacks bottom near 40 and the reclaim of 50 marks the dip ending, which is why RSI-crossing-50 scans exist alongside the oversold ones. The standard pairing is a long-term trend filter: RSI under 40 above the 200-day average is a pullback; the same reading below it is a decline in progress. The way RSI hurts people is simple: oversold is not a floor and overbought is not a ceiling. A stock in real trouble can hold RSI under 30 for months, getting more oversold as it halves; a strong trend can ride above 70 for weeks. The reading describes the recent past — it says the move has been one-sided, not that it must stop. Waiting for the cross back through a level asks for evidence, which is the difference between a signal and a hope. Its nearest sibling is MFI, which runs the same construction weighted by money traded — RSI counts the sessions, MFI weighs them. The stochastic measures something different despite the similar scale: where the close sits in the recent range, not how large the moves were. ## In Sift Written as `rsi(14)`. A working scan — stocks whose RSI reclaimed 30 in the last three sessions while holding the 200-day average: ```sift where rsi(14) crossed above 30 within 3 bars and close > sma(200) ``` 0 of the 500 most-traded NSE stocks match today, as of 2026-08-20. ## Scans that use it - [RSI oversold turning up](https://patternsradar.com/screener/rsi-oversold-turn.md): RSI crossing back above 30 in the last three sessions while the stock still holds its 200-day average — a pullback, not a collapse. - [RSI overbought](https://patternsradar.com/screener/rsi-overbought.md): RSI above 70 while the stock is still trending — stretched, and worth knowing about either way. - [RSI reclaiming 50](https://patternsradar.com/screener/rsi-50-reclaim.md): RSI crossing back above its midline in a stock that never lost its long-term trend. - [CCI overbought](https://patternsradar.com/screener/cci-overbought.md): CCI above +100 with RSI agreeing — stretched by two different measures at once. - [Williams %R overbought](https://patternsradar.com/screener/williams-overbought.md): Closing in the top fifth of its two-week range with RSI above 70 — extended on both clocks. - [Strong but not overbought](https://patternsradar.com/screener/strong-and-quiet.md): Three-month gains with RSI still under 65 — room to run without chasing. - [Strong directional trend](https://patternsradar.com/screener/adx-strong-trend.md): ADX above 30 with buyers in control and the averages stacked — a trend worth trading. - [Rate of change leaders](https://patternsradar.com/screener/roc-momentum.md): Ten percent rate of change with RSI still under 70 — acceleration, not exhaustion. - [Pullback in an uptrend](https://patternsradar.com/screener/pullback-in-uptrend.md): RSI under 40 in a stock still above its 200-day — weakness for sale inside strength. - [Hammer while oversold](https://patternsradar.com/screener/hammer-oversold.md): A long lower wick after a decline, with RSI still under 40. - [Shooting star after a run](https://patternsradar.com/screener/shooting-star-top.md): A long upper wick with RSI above 60 — buyers tried and could not hold it. - [Bullish harami](https://patternsradar.com/screener/bullish-harami.md): A small up-day held inside the previous big down-day, with RSI already washed out. - [Bearish harami](https://patternsradar.com/screener/bearish-harami.md): A hesitation candle inside a big up-day, high enough on the chart to matter. - [Large-cap pullback](https://patternsradar.com/screener/mega-cap-dip.md): Stocks above ₹20,000 crore market cap washed out below RSI 40 — size as the quality filter. - [IT stocks in an uptrend](https://patternsradar.com/screener/it-stocks-uptrend.md): The Information Technology sector filtered to names above the 200-day with momentum intact. ## Common questions ### What is a good RSI level for buying? The textbook answer is below 30, but context does most of the work. In trending stocks pullbacks bottom near RSI 40, and RSI 35 above a rising 200-day average is a very different situation from RSI 35 in a downtrend. Rather than trust any threshold, the hit-rate replay on each scan page shows how a given level has actually resolved on NSE history. ### Can RSI stay overbought for a long time? Yes, and in the strongest stocks it routinely does — an established uptrend can hold RSI above 70 for weeks while price keeps climbing. That is why selling every overbought print exits the best trends early. Overbought describes the recent past as one-sided; it is a description, not a deadline. ### Why is 14 the standard RSI period? Because Wilder used 14 in his 1978 book and the default stuck. Shorter periods make RSI touch its extremes more often; longer ones smooth it toward the midline. Fourteen is a convention with decades of shared usage behind it, which itself has value — the levels everyone watches are the ones behaviour anchors to.