- Wilder's formula and calculation of the RSI with RS, RMA smoothing and clear numerical examples to understand each step.
- Practical interpretation: 30/70 levels, 50 crossover, 40–90 and 20–60 adjustments depending on the market phase.
- Effective strategies: divergences (classic and hidden), failure oscillations, and crossovers between fast and standard RSI.
- Use responsibly: combine with other indicators, adapt periods and manage risk in leveraged products.
The Relative Strength Index (RSI) is one of those indicators that appears on virtually every trading platform because summarizes in a single number the speed and change of pricesIt moves between 0 and 100, and is used to detect overbought and oversold moments, possible reversals and the strength of a trend.
If you're wondering how it's calculated and how to interpret it, here's a complete guide: from the classic Welles Wilder formula including step-by-step examples, advanced reading methods (divergences, failure oscillations), differences with MACD, market configurations, and practical tricks to incorporate it into your trading without getting confused.
What is the RSI and what is it used for?
The RSI is a momentum oscillator designed by J. Welles Wilder that quantifies the strength of recent price movements. Its scale ranges from 0 to 100 and, in practical terms, High values suggest buying pressure While low values indicate selling pressure. Furthermore, it's incredibly visual: at the bottom of the chart you'll see its line oscillating, allowing you to quickly identify key areas.
It is worth remembering three basic ideas: above 70 is usually considered overbought, below 30 oversold, and around 50 we have a neutral zone that helps to read the underlying bias. These figures are not dogmaAnd indeed there are useful adjustments depending on the market phase: in uptrends 40-90 is often used, and in downtrends 20-60, to avoid premature signals.
RSI formula and calculation method
The RSI is constructed from the relationship between average gains and losses over a chosen period (the standard is 14). The canonical formula is: RSI = 100 − (100 / (1 + RS)), where RS is the relative strength calculated as average gain / average loss of the period under consideration.
Wilder proposed a specific smoothing technique (similar to an exponential moving average) to make the indicator respond stably. On modern platforms, this smoothing is usually implemented as an RMA or modified exponential moving average. which reduces abruptness and “noise” without excessively delaying the signal.
- Calculate the daily change in the closing price (up and down).
- Separate gains (excluding declines) and absolute losses (excluding gains).
- Obtain the average profit and average loss for the period (for example, 14).
- Find RS = average gain / average loss.
- Apply RSI = 100 − 100 / (1 + RS) and you will have the value of the oscillator.
In practice, you won't have to do it manually: almost all platforms come with the RSI "as standard". Even so, Understanding the calculation helps you interpret things better. what each reading means and why it may vary when the period changes.
Practical example: calculating the RSI step by step
To illustrate the process, look at this example with 14 days (a very common period). You'll see the closing, the change, and how profits and losses are separated. With this data, the RS and the RSI are obtained. of the last day.
| Daytime | Closing | Change | Gain | Lost |
|---|---|---|---|---|
| 1 | 50 | - | - | - |
| 2 | 52 | +2 | 2 | 0 |
| 3 | 51 | −1 | 0 | 1 |
| 4 | 53 | +2 | 2 | 0 |
| 5 | 55 | +2 | 2 | 0 |
| 6 | 54 | −1 | 0 | 1 |
| 7 | 56 | +2 | 2 | 0 |
| 8 | 58 | +2 | 2 | 0 |
| 9 | 57 | −1 | 0 | 1 |
| 10 | 59 | +2 | 2 | 0 |
| 11 | 60 | +1 | 1 | 0 |
| 12 | 61 | +1 | 1 | 0 |
| 13 | 60 | −1 | 0 | 1 |
| 14 | 62 | +2 | 2 | 0 |
Adding it up, we have 16 gains and 4 losses over 14 sessions; if we use the simple average to start, the average gain would be 16/14 and the average loss 4/14. Hence, RS ≈ 3,93, and therefore, RSI ≈ 79,7. A figure above 70 suggests overbought conditionsThis doesn't necessarily mean selling, but it does mean monitoring for potential price corrections.
Another classic example, this time with 9 periods, starts with the known closing prices of a stock (for example, a series like 6,02; 5,95; 5,95; 5,98; 5,83; 5,81; 5,86; 6,06; 6,09; 6,09). The daily variations are calculated, increases and decreases are separated, and they are averaged for that period. With an approximate RS of 1,2917The resulting RSI is around 56,36 points, an intermediate zone closer to overbought than oversold.
RSI Interpretation: Key Zones and Signals
The most common interpretation relies on three horizontal levels: 30, 50, and 70. Above 70, the price is usually considered "hot"; below 30, "cold." And around 50, we can distinguish between bullish and bearish momentum. Above 50, buying power prevailsThe seller was below.
In trending markets, it's advisable to adjust the bands to avoid exiting the market too early. During upward phases, many traders shift the useful band to 40-90 (extreme readings are required to consider the market overbought), and during downward phases to 20-60 (lower readings are tolerated without indicating extreme oversold conditions). This context adjustment reduces false signals.
Furthermore, the 30 and 70 crossovers are signals, but the 50 crossovers often act as confirmations: if the RSI crosses 50 upwards after a bounce from 30, The upward continuation hypothesis is reinforcedIf it loses 50 after a rejection at 70, the bearish bias is reinforced.
It's also useful to modulate the signal's "speed" by modifying the levels. For example, you can consider 70 as fast overbought, 80 as more conservative, and 90 as very strict; and 30, 20, and 10 as oversold, respectively. The more extreme the levels, the fewer signals. You will get them, but probably more select ones.
Advanced signals: divergences, convergences, and fault oscillations
One of the great strengths of the RSI is that it reveals divergences between price and momentum. If the price makes new highs but the RSI doesn't follow suit (lower highs), a bearish divergence appears; if the price makes new lows but the RSI makes higher lows, a bullish divergence is present. Both can anticipate twists or at the very least, a correction.
There are also hidden divergences, which tend to be continuation patterns: in an uptrend, the price makes higher lows while the RSI makes lower lows (a bullish resumption signal); in a downtrend, lower highs in the price and higher highs in the RSI suggest continuing with the bearish bias. They are highly valued by trend traders.
Another pattern to watch is Wilder's failure swing, which disregards price action and relies solely on the RSI. In a bullish version: falling below 30, bouncing back above 30, retracing without falling below 30, and then breaking above the previous RSI high; in a bearish version: rising above 70, retracing below 70, bouncing back without falling above 70, and then breaking below the previous low. They are clean and autonomous patterns.
Don't forget double divergence either: sometimes the first signal is not enough to stop the trend and a second divergence (of the same sign) greatly reinforces the probability of a reversal. Patience and confirmation They usually make the difference here.
RSI versus MACD and other indicators
RSI and MACD both look "backward" in the sense that they are derived from historical data, but their focuses differ. The MACD compares moving averages of price and measures acceleration and deceleration of the trend; the RSI focuses on the balance between recent rises and falls. Combining them adds perspectiveThe MACD suggests the trend context and the RSI confirms or warns of exhaustion.
As a limitation, the RSI does not incorporate volume or order flow dimensions, so it makes sense to use it in conjunction with volume tools (e.g., OBV) or other similar tools. complementary indicators to validate scenarios.
RSI period and routine adjustments
The default period (14) is a standard due to its balance between responsiveness and stability. Even so, many traders explore 9 for greater sensitivity or 25 for smoothing. The shorter the period, the more signals (and more noise); the longer the signal, the fewer signals but the more filtered they are.
A couple of useful references: on a 1-minute chart with an RSI of 9, the reading roughly reflects the last 9 minutes; on a 5-minute chart with an RSI of 14, about 70 minutes; on a daily chart with an RSI of 25, around 25 sessions. Adjust the period to the time frame and the asset. that you work.
Trend lines on the RSI itself
Just like with price, you can draw trend lines over the RSI's peaks and troughs. By linking two or three relevant points and watching for breakouts, you'll often see that the RSI breakout... It anticipates the priceThis provides an early signal to position yourself or tighten stops.
Use of RSI in indices, forex, and other markets
The RSI is versatile and adapts to stocks, indices, currencies, commodities, such as the Brent oil...and even cryptocurrencies. In indices (e.g., the S&P 500), it can help close long positions when the index stretches towards 75-80 with additional signs of exhaustion; in forex, divergences in H1 or H4 frames They are a classic for hunting reversals or pullbacks; in crypto, many traders prefer slightly longer periods (such as 21) to tame high volatility.
A typical workflow for indices includes: adding the RSI (14) to the chart, marking levels 30/70 (or adapting them), waiting for a signal (extreme, 50 crossover or divergence) and confirming with another tool (moving averages, Bollinger Bands, volume, market structure…). Confirmation reduces false positives.
Another useful idea is to exploit the correlation between assets: if you detect a strong divergence with the RSI in a widely followed index, review closely correlated assets because, sometimes, The signals travel through families of assets and reinforce reading.
Important: If you trade leveraged products such as CFDs, remember that they are complex and may not be suitable for everyone. There is a high risk of rapid loss. because of leverage; assess whether you understand how they work and whether you can take the risk.
How to add and configure RSI on your platform
On platforms like MetaTrader, the typical path is: Insert → Indicators → Oscillators → Relative Strength Index. Then you can choose the "Length" (periods), the "Source" of the data (default close), and the levels. With the default settings, you can now workand it's always possible to adapt them later.
Useful configuration details: RSI Length (number of bars for calculation), Source (close, open, high, low or average price), option to show divergences if your platform allows it and the type of internal smoothing (modified RMA/EMA is usually Wilder's standard). Find out what's under the hood to interpret with discernment.
Strategies with RSI: crossovers, levels and combinations
Basic and effective signals: an RSI that comes out of oversold territory (rises above 30) and breaks 50 upwards has an added probability of continuation; symmetrically, a drop from overbought territory (loss of 70) followed by a downward break of 50 reinforces the bearish bias. The levels function as filters. signal quality.
Another common combination is to overlay a fast RSI (for example, 5) on the standard RSI (14) and watch for crossovers between the two, especially when the faster one crosses upwards near 30 or downwards near 70. This approach captures turns in advance. at the cost of greater sensitivity.
To modulate the speed, you can use "fast/medium/slow" levels. For example, consider fast overbought at 70, normal at 80, and slow at 90; and fast oversold at 30, normal at 20, and slow at 10. More extremity = fewer signals but more demanding.
Don't forget to read the RSI using trend lines and look for double divergence when you want particularly strong signals. Integrating price patterns (support, resistance, candlesticks) multiplies the power. The RSI is rarely a silver bullet on its own..
Advantages, limits and precautions
- Advantages: quick overbought/oversold reading, bias confirmation with 50, divergence detection and multi-sector application (indices, currencies, commodities, crypto…).
- More advantages: easy to interpret, useful for intraday and scalping, combines well with MACD, Stochastic, Bollinger Bands or pivot points for comprehensive strategies.
- Limitations: It can generate false signals in sideways ranges, it does not include volume, and in strong trends, it can get "stuck" overbuying/overselling for a period of time.
- Precautions: adapt periods and levels to the asset and time frame, validate with another tool and manage risk (stops, position size, written plan).
Quick FAQ
Can it be applied to any asset? Yes. It's a versatile momentum oscillator for stocks, bonds, indices, commodities, and cryptocurrencies.
What is a “good” RSI for trading? It depends on the market and strategy. Trending, above 50 confirms strength Bullish and below 50 bearish strength; for mean reversion, the 30/70 zones are your allies.
Does it work on its own? It can provide very valid clues, but its best use is in conjunction with other signals: price structure, volume, moving averages or MACD.
Is it a lagging indicator? Yes, like all technical indicators derived from price. Even so, their divergences and crossings They offer highly valued operational signals, especially if they are confirmed.
Mastering the RSI is a matter of practice and context: understand its formula, adapt periods and levels to the asset, combine it with a confirmation, and apply discipline to risk management; in this way, This oscillator will help you read the momentumto detect depletion and fine-tune inputs and outputs with criteria.
