RSI —
Relative Strength Index
The momentum oscillator that tells you when buying or selling pressure is stretched to the limit. Overbought, oversold, divergences, and more.
First — Why This Matters
The Rubber Band Effect
Stretch a rubber band between your fingers. Pull it further... further... eventually it snaps back. The further you stretch it, the harder it snaps. RSI measures how far the market's rubber band is stretched.
When buying pressure has been relentless (RSI above 70), the rubber band is stretched to the upside — a snap back (pullback) becomes likely. When selling has been extreme (RSI below 30), it's stretched to the downside — a bounce becomes likely. RSI doesn't predict the future, but it tells you when the pressure is unsustainable.
Real scenario: GBP/USD has rallied 400 pips in 5 days. RSI hits 82. Your friend says "buy, it's going to the moon!" But you see the stretched rubber band. You wait. Next day: 120-pip pullback. You buy the dip at a much better price — because RSI warned you the rally was exhausted.
01 — The Concept
What Is RSI?
The Relative Strength Index is a momentum oscillator that measures how fast and how strongly price is moving. It oscillates between 0 and 100.
Created by J. Welles Wilder in 1978, RSI answers one question: "Is the recent buying or selling pressure sustainable?" When momentum stretches too far in one direction, it often snaps back.
Overbought (Stretched Up)
Think of a rubber band pulled too far upward. Buyers have been dominant for too long — the "snap back" (price pullback) becomes more likely. This doesn't mean sell RIGHT NOW — but it means be careful about buying at these levels. The rubber band could snap any moment.
Neutral (No Man's Land)
The rubber band is relaxed — not stretched in either direction. Buyers and sellers are roughly equal. This is the waiting zone. When RSI breaks above 50, it's like the rubber band starting to stretch upward. Below 50, it's stretching down.
Oversold (Stretched Down)
The rubber band is pulled too far downward. Sellers have been relentless — a bounce becomes more likely. This is where smart traders start WATCHING for buy signals. Not buying blindly — but getting ready for the snap back.
02 — Under the Hood
How RSI Is Calculated
Step through Wilder's original formula. Each step builds on the last. By the end, you'll understand exactly what the number means.
Step 1: Did Price Go Up or Down?
Simple — compare today's closing price to yesterday's. If it went up, write down the gain. If it went down, write down the loss (as a positive number). Do this for every day in the period.
Change = Close[today] - Close[yesterday]03 — See It Live
Interactive RSI Chart
Price action on top, RSI below. Toggle between periods (7, 14, 21) and see how sensitivity changes. Watch for the dots where RSI enters overbought or oversold territory.
Top panel: Price action. Bottom panel: RSI oscillator (purple line). Red zone (above 70) = overbought. Green zone (below 30) = oversold. Period 14 is the standard — the best balance of sensitivity and reliability.
04 — The Trap
Overbought ≠ Sell. Oversold ≠ Buy.
The #1 mistake new traders make with RSI. This is so important it gets its own section.
In strong trends, RSI can stay overbought (above 70) or oversold (below 30) for weeks or even months. Selling just because RSI is 75 in a raging bull market will get you destroyed.
❌ The Wrong Way
"RSI is 72, I'm shorting!" → Gets crushed as RSI stays above 70 for 3 weeks during a bull run.
✅ The Right Way
RSI confirms what other tools show. Use it with S/R, trendlines, and price action. Never trade RSI alone.
05 — Divergence
When Price & RSI Disagree
Divergence is one of the most powerful signals in all of trading. It reveals hidden weakness (or strength) that price alone doesn't show.
Bullish Divergence
Price makes lower lows but RSI makes higher lows. The selling momentum is weakening even though price is still falling. This often precedes a reversal upward — a potential buying opportunity.
06 — Read the RSI
Spot the Signal Game
5 charts. Each shows a different RSI condition. Identify whether it's overbought, oversold, bullish momentum, bearish momentum, or divergence.
What is the RSI telling you?
07 — Assessment
RSI Mastery Quiz
7 questions. Theory, calculation, and practical application.
Question 1 of 7
RSI measures:
Question 2 of 7
An RSI reading above 70 typically indicates:
Question 3 of 7
In the RSI formula, what does RS (Relative Strength) represent?
Question 4 of 7
Bullish RSI divergence occurs when:
Question 5 of 7
The standard RSI period is:
Question 6 of 7
RSI is most useful in which type of market?
Question 7 of 7
If RSI is hovering around 50, this suggests:
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