RSI is one of the most used tools in technical analysis. It is also one of the most misread. Traders treat 70 as a sell signal and 30 as a buy signal. That habit has cost portfolios real money. This article explains what the indicator does, how it feeds into the Stoxcraft TrendMeter, and the single market condition where RSI becomes a trap.
What the RSI indicator measures
RSI stands for Relative Strength Index. The name is easy to misread. It does not compare one stock to another. It compares a stock to itself. It measures how much the stock has been winning versus losing. That comparison covers a set period of time, typically 14 trading days.
The output is a number between 0 and 100. A score near 100 means the stock has been closing up almost every day. A score near 0 means it has been closing down almost every day. A score near 50 means gains and losses are roughly in balance.
How RSI is calculated over 14 trading days
The math behind RSI is straightforward when broken into steps. Two inputs drive the whole calculation: average gains and average losses.
The formula keeps the output between 0 and 100. After the first 14 days, Wilder used a smoothing method. Each updated average blends the prior average with the latest day's data. Recent price action always carries more weight than older data.
The two levels almost every trader watches
These two numbers became the most recognized thresholds in technical analysis. They are also the most widely misapplied.
What the RSI score means in plain terms
The 70 and 30 rule: what Wilder's book really said
Most traders hear "overbought" and think "sell." They hear "oversold" and think "buy." It is a natural first reading. But Wilder pushed back on it in his own text. He wrote that RSI above 70 signals a reaction is likely, not that one is imminent. Those are very different statements.
The 70 and 30 levels work well in one specific market type: range-bound, sideways markets. When a stock has no clear trend and bounces between a price floor and a ceiling, RSI extremes do tend to precede reversals. Buyers step in near 30. Sellers take profit near 70. The system works as intended.
Change the market condition, and the logic falls apart entirely.
How RSI fits into the Stoxcraft TrendMeter
The Stoxcraft TrendMeter is a short-to-mid-term technical score built from four inputs. RSI carries approximately 30% of the total weight.
Readings above 70 do not push the TrendMeter higher. The RSI contribution is capped at that level. The remaining three components, MACD at approximately 25%, one-month price performance at approximately 30%, and upside to the 52-week high at approximately 15%, all contribute alongside it. No single input drives the outcome.
This is how RSI should be used: not as a standalone trigger, but as one part of a multi-input picture. The full Stoxcraft scoring methodology is explained in detail on the Stoxcraft scoring system blog post.
The one market condition where RSI misleads you every time
This is the part most textbooks skim past. RSI fails in one environment: a strong, sustained trend. Not occasionally. Not in edge cases. It fails structurally. The tool was not built to handle this condition.
What happens to RSI during a strong uptrend
When a stock enters a powerful bull run, up days stack against each other. The average gain keeps getting refreshed with strong closes. The average loss barely registers. The ratio of gains to losses climbs. RSI climbs with it.
Once RSI crosses 70, the standard interpretation says the stock is overbought. But if the trend is strong and real, RSI does not reverse. It stays above 70 for weeks. Sometimes months. The stock keeps going up the entire time.
A trader waiting for RSI to drop before buying is waiting in vain. A trader shorting because RSI crossed 70 is fighting a trend that has no intention of turning. The RSI kept flashing the warning. The price kept climbing.
Nvidia's RSI during the 2023 and 2024 AI surge
Nvidia (NVDA) is the clearest modern example of this failure mode. Between the start of 2023 and March 2024, Nvidia surged nearly 550%, repeatedly crossing into overbought RSI territory along the way. During that entire run, NVDA's RSI spent extended stretches above 70. Each time the threshold was crossed, the textbook signal said sell or wait. Each time, the stock continued higher.
A trader who sold each time NVDA's RSI hit 80 during those two years missed back-to-back annual gains of 239% in 2023 and 166% in 2024. The indicator captured the momentum perfectly. The mistake was treating that momentum as a reversal signal rather than a trend description.
Nvidia is not the only case. Meta Platforms (META) spent long stretches of its 2023 recovery in overbought RSI territory while posting one of its strongest years on record. Tesla (TSLA) ran above RSI 70 for weeks at a time during its surge in 2020. The pattern is identical across all of them. A strong trend keeps refreshing the average gain. RSI stays elevated. The stock does not care.
Where RSI performs best: sideways and recovering markets
Flip the scenario. A stock is going nowhere. It bounces between a price floor and a price ceiling. No clear trend exists in either direction. This is where RSI earns its reputation.
The same logic applies during market corrections. When a fundamentally sound stock drops sharply in a broad selloff, RSI below 30 can flag that selling has become excessive relative to the recent price history. The business has not broken. The stock has been dragged down by fear. RSI picks up that pressure.
RSI divergence also adds value in these conditions. If a stock makes a new low in price but RSI makes a higher low, the selling force is weakening. The price looks bearish. The momentum data disagrees. That gap is worth noting, especially when no strong downtrend is driving the action.
What to pair with RSI to get a cleaner signal
RSI answers one specific question: how strong and fast has recent price movement been? It does not tell you whether a trend exists, how durable it is, or whether a breakout is underway. Other tools answer those questions.
The Stoxcraft TrendMeter applies RSI alongside MACD, one-month price performance, and 52-week high distance. No single input carries the decision. That is not a design compromise. That is the right way to use momentum data.
The RSI level the Stoxcraft BuyMeter treats as the cleanest entry point
Most traders ignore RSI at 50. It looks neutral. But the Stoxcraft BuyMeter treats RSI near 50 as the most attractive entry condition, not RSI near 70.
The logic is direct. An RSI of 50 means the stock is neither overextended to the upside nor beaten down by sustained selling. It has not been chased by momentum traders. It has not been abandoned by panicked sellers. It sits in a balanced zone, historically a cleaner starting point for a new position.
A stock with RSI at 48, rising MACD, and strong analyst consensus is a very different setup from the same stock with RSI at 76. The first is a measured entry into a building move. The second is a momentum chase at an elevated level. Both can produce gains. The risk profiles are completely different.
RSI as a starting point, not a trading finish line
The RSI indicator has survived nearly five decades because it captures something real: the speed and force of recent price action. That information is useful. But it is one input, not a complete strategy.
RSI above 70 in a strongly trending stock is not a sell signal. It is confirmation that short-term momentum is elevated. That is a different piece of information. RSI below 30 in a stock caught in a structural downtrend is not an automatic buy. It may just reflect a trend that has further to fall.
Used correctly, RSI tells you where momentum stands at a point in time. It does not tell you where price goes next. The Stoxcraft screener runs RSI alongside three other TrendMeter inputs across the full stock universe in real time. The combined score is consistently more reliable than any single reading on its own.
Wilder built RSI to describe momentum. It does that well. The trap is treating a description as a direction.
