What Is RSI?
The Relative Strength Index (RSI) is a momentum oscillator developed by J. Welles Wilder Jr. It ranges from 0 to 100 and measures the speed and change of price movements. The standard RSI uses 14 periods and is plotted as a single line beneath the price chart.
How RSI Works
RSI calculates the ratio of average upward price changes to average downward price changes over the lookback period. Key levels:
- Above 70 — Overbought territory (not necessarily a sell signal, but caution warranted)
- Below 30 — Oversold territory (not necessarily a buy signal, but bounce potential)
- 50 line — The momentum midpoint; crossing above is bullish, crossing below is bearish
RSI divergences are the most powerful signal: when price makes a new high but RSI makes a lower high, bullish momentum is fading and a reversal may be imminent.
Why It Matters for Traders
RSI is one of the most popular and versatile indicators in crypto. Beyond overbought/oversold readings, RSI divergences on the daily timeframe have reliably signaled major trend reversals across Bitcoin cycles. In trending markets, RSI staying above 40 (uptrend) or below 60 (downtrend) confirms trend strength.
How Perps Traders Use This
For CEX perpetual futures, treat rsi (relative strength index) as context around entries, exits, and risk, not as a standalone signal. Pair it with funding, open interest, and liquidation heat so one indicator does not drive the whole book.
Formula and Worked Example
Example numbers only (not a live quote).
If your account equity is $10,000 and you risk 0.5% per idea, the cash risk budget is $50. With a stop 1% away from entry on a linear USDT-margined perp, notional size is about $5,000 before leverage optics. Size from stop distance first, then pick leverage that fits the margin mode.
Common Mistakes
- Treating a single print of rsi (relative strength index) as a trade signal without checking funding, open interest, and your liquidation price.
- Mixing venue conventions (coin-margined vs USDT-margined, cross vs isolated) and reading the wrong mark.
- Copying example numbers from a glossary into live size without checking the current book depth and fee schedule.
- Ignoring related terms that change the meaning of the print on a given day.
