RSI Indicator Explained With Examples

What the RSI is and why traders use it

The Relative Strength Index (RSI) is a momentum oscillator that measures the speed and change of price movements. Created by J. Welles Wilder, it ranges from 0 to 100 and is most often used to identify overbought and oversold conditions, detect divergences, and help time entries or exits.

Common use cases include relative strength index trading on stocks, ETFs, and other liquid markets. In fast-moving market headlines — for example, when Abbott Labs shares jump 12% after a strong quarter — the RSI can help you see whether that move is stretched or still has room to run.

The formula (plain and simple)

• Step 1: Compute the price changes (gains and losses) for each period.
• Step 2: Calculate average gain and average loss (Wilder’s smoothing for a 14-period RSI is standard).

Key formulas:

• RS (Relative Strength) = Average Gain / Average Loss
• RSI = 100 - (100 / (1 + RS))

Wilder’s smoothing (14 periods):

• First Average Gain = sum of gains over first 14 periods / 14
• First Average Loss = sum of losses over first 14 periods / 14
• Subsequent AvgGain = [(PrevAvgGain * 13) + CurrentGain] / 14
• Subsequent AvgLoss = [(PrevAvgLoss * 13) + CurrentLoss] / 14

This produces a smoother, more responsive oscillator than a simple moving average of gains/losses.

Interpreting RSI: overbought oversold RSI and other signals

• Traditional thresholds: RSI > 70 = overbought; RSI < 30 = oversold.
• For stronger trends, some traders use 80/20 to reduce false signals.
• Divergence: When price makes a new high but RSI fails to make a new high (bearish divergence), it can signal weakening momentum. The opposite is bullish divergence.
• Trend confirmation: In strong uptrends, RSI often stays above 40-50; in downtrends, it may remain under 50-60.

No single reading should be traded in isolation — combine RSI with trend context, support/resistance, and volume.

Worked 14-period example (step-by-step)

This is a hypothetical illustration; numbers are illustrative, not market advice.

Assume daily closing prices for a stock over 15 days. Compute daily change = today_close - yesterday_close.

Day 1–14 (closing price changes): +0.50, +0.30, -0.20, +0.40, +0.10, -0.50, +0.20, +0.80, -0.10, +0.60, +0.30, -0.40, +0.10, +0.20

Step A — Calculate average gain and average loss for the first 14 periods

• Sum gains: add positive changes only = 0.50+0.30+0.40+0.10+0.20+0.80+0.60+0.30+0.10+0.20 = 3.50
• Sum losses: add absolute values of negative changes = 0.20+0.50+0.10+0.40 = 1.20
• AvgGain (first) = 3.50 / 14 = 0.25
• AvgLoss (first) = 1.20 / 14 ≈ 0.0857

Step B — Compute RS and RSI

• RS = AvgGain / AvgLoss = 0.25 / 0.0857 ≈ 2.917
• RSI = 100 - (100 / (1 + 2.917)) = 100 - (100 / 3.917) ≈ 100 - 25.54 = 74.46

Interpretation: an RSI of ~74 suggests the market is in overbought territory by traditional 70 threshold, but you would check the trend (is price trending strongly?), look for divergence, and consider time frame before acting.

Step C — Rolling to day 15 (how smoothing updates)

Suppose day 15 change = -0.30 (a loss). Use Wilder’s smoothing to update:

• NewAvgGain = [(0.25 * 13) + 0 (since day15 gain = 0)] / 14 = (3.25) / 14 ≈ 0.2321
• NewAvgLoss = [(0.0857 * 13) + 0.30] / 14 = (1.1141 + 0.30) / 14 ≈ 0.1010
• NewRS = 0.2321 / 0.1010 ≈ 2.298
• NewRSI = 100 - (100 / (1 + 2.298)) ≈ 100 - (100 / 3.298) ≈ 100 - 30.31 = 69.69

So the RSI fell from ~74 to ~70 after one losing day. This shows how Wilder smoothing reduces noise but still responds to new data.

Practical tips for retail traders

• Choose timeframe to match your trade horizon: 14-period RSI on daily charts is common for swing trading; shorter periods (e.g., 7) make RSI more sensitive for intraday strategies.
• Avoid trading a single cross of 70/30 — look for confirmation (price action, volume, moving averages).
• Watch for divergence as a higher-probability signal than just an overbought/oversold number.
• Use different thresholds in strong trends: in a strong uptrend, consider buying on RSI pullbacks to 40–50 rather than waiting for <30.
• Manage risk: always define stop-loss and position size before entering — RSI does not give stop levels.

Common pitfalls and how to avoid them

• False signals: RSI can remain overbought for extended periods. Avoid selling solely because RSI > 70 in a strong uptrend.
• Overfitting thresholds: Don’t optimize thresholds excessively on historical data; they may not generalize.
• Ignoring trend context: An oversold RSI in a downtrend is more likely to be a signal to trade with the trend (short) than to buy immediately.

Where to practice

You can test the RSI and other strategies risk-free in AIYUG's free paper-trading race: https://aiyug.us/race. Practical, repeated testing on paper helps you learn typical behaviors and signal reliability without risking capital.

This article explains mechanics and shows a worked example, but it is educational only. It is not financial advice or a guarantee of results.