RSI and MACD: what they actually measure (and what they don't)

The myth of the universal indicator

RSI and MACD are ubiquitous. Open any charting platform, apply the defaults, and you'll see them instantly. The problem is that their ubiquity has turned them into superstition: traders watch for the same levels, which creates the same reactions, which occasionally creates the appearance of self-fulfilling prophecy — but not reliably enough to trade on.

Understanding what the math actually says is the antidote to both blind faith and blind rejection.

RSI: measuring recent gain vs. recent loss

The Relative Strength Index (RSI), developed by J. Welles Wilder in 1978, measures the ratio of average gains to average losses over a lookback period (typically 14 candles).

The formula (simplified): RSI = 100 – (100 / (1 + RS)) Where RS = Average of gains in period / Average of losses in period

An RSI of 70 means gains have dominated losses for 14 periods by a ratio of approximately 2.3:1. An RSI of 30 means losses have dominated by the same ratio.

What it actually measures: Momentum. RSI tells you whether a price has been moving up or down consistently relative to its own recent history. It does not tell you whether the current price is "fair" or whether the trend will continue.

The classic misapplication: Using RSI overbought/oversold as buy/sell signals in isolation. During a strong bull trend, RSI can stay above 70 for weeks. During a bear trend, it can stay below 30 for equally long. Selling a coin just because RSI hit 80 is a reliable way to miss the remainder of a strong trend.

A better use: RSI divergences — when price makes a new high but RSI makes a lower high — are weakly predictive of trend exhaustion. Still not a reliable timing tool, but more informative than the raw level.

MACD: tracking two moving averages

MACD (Moving Average Convergence Divergence) tracks the difference between a 12-period and 26-period exponential moving average (EMA), and separately tracks a 9-period EMA of that difference (the "signal line").

The three components:

• MACD line: EMA(12) – EMA(26)
• Signal line: EMA(9) of the MACD line
• Histogram: MACD line – Signal line

When the MACD line crosses above the signal line, the histogram turns positive — the popular "bullish crossover." When it crosses below, the histogram turns negative.

What it actually measures: Trend momentum over two different timeframes. The 12-period EMA responds faster to recent price action than the 26-period EMA. When the faster EMA pulls ahead of the slower one, it indicates that recent momentum has accelerated.

The lag problem: Both EMAs are backward-looking by construction. By the time a MACD crossover occurs, the price move that caused it is already underway. In fast-moving markets, MACD crossovers often occur near the end of a move rather than the beginning — entering on a MACD crossover in a volatile altcoin frequently means buying the exhaustion.

How Coinblockers weights these indicators

In the composite score, RSI and MACD each receive a weight of 0.35 within the technical factor component (which itself is 30% of the overall score). Neither is treated as a primary signal. They're inputs to a weighted average that also includes volume trend and moving average spread.

Z-scoring is applied before weighting: the raw RSI value is less meaningful than "RSI is 1.8 standard deviations higher than its 90-day average." This adjustment helps reduce the regime-dependence problem — a bull market inflates RSI readings, but a z-score measures deviation from the asset's own recent baseline.

The honest summary

RSI and MACD are useful for one thing: identifying relative momentum within an asset's own history. They are not useful for predicting reversals with any reliability, and they are not useful for comparing momentum across different assets with different volatility profiles.

Use them as one input among many. Never use either one alone.