--- title: "Rank Correlation Index: Formula, Meaning" description: "Applies Spearman's rank correlation to price: it correlates the rank of each recent price with the rank of its time order. A value near +100 means prices..." canonical: https://www.getswoopr.com/indicators/momentum/rank-correlation-index/ source: "Swoopr Investment: https://www.getswoopr.com" --- ## Direct Answer > Applies Spearman's rank correlation to price: it correlates the rank of each recent price with the rank of its time order. A value near +100 means prices are consistently rising over the window, and near -100 consistently falling. It ranges from -100 to +100. # Rank Correlation Index: Formula, Meaning, Signals, Examples and How to Use It ## How Is Rank Correlation Index Calculated? Applies Spearman's rank correlation to price: it correlates the rank of each recent price with the rank of its time order. A value near +100 means prices are consistently rising over the window, and near -100 consistently falling. **Formula:** `RCI = 100 * (1 - 6 * Sum(d^2) / (n * (n^2 - 1))), where d is the difference between the price rank and the time rank` **Inputs:** - Closing prices - Window length n (periods such as 9 are used) - Price rank and time rank within the window **Worked example.** With 9 prices and a sum of squared rank differences of 20, the rank correlation is 83.3%. The inputs are illustrative numbers, not market data. **Reading it.** It ranges from -100 to +100. Readings near the top indicate prices ordered in a rising sequence, and near the bottom a falling one. High and low thresholds are often used to flag trend extremes. **Limits.** Using ranks ignores the size of price moves, so a small drift and a large move rank identically. Ties and short windows make the value jump around. ## What is Rank Correlation Index? Applies Spearman's rank correlation to price: it correlates the rank of each recent price with the rank of its time order. A value near +100 means prices are consistently rising over the window, and near -100 consistently falling. ## How to use Rank Correlation Index It ranges from -100 to +100. Readings near the top indicate prices ordered in a rising sequence, and near the bottom a falling one. High and low thresholds are often used to flag trend extremes. A reading alone is never a buy or sell signal; it needs context from price structure, volume, volatility and the broader market regime. ## Strengths - Correlating price rank with time rank yields a bounded value that reflects how consistently prices ordered upward, not how far they moved. - Ranking removes the influence of outliers, so a single spike changes one rank position rather than stretching the whole calculation. - Reproducible when the formula and data convention are fixed. ## Weaknesses and limitations - Time ranks are a fixed sequence, so the value measures only how closely price order follows time order, with no link to volatility or volume. - The value moves in discrete steps set by the window length, so a short window offers only a coarse set of possible readings. - Correlated indicators can create false confidence by repeating the same underlying information. ## Editorial and risk note This page is educational content, not individualized investment advice. It should not imply guaranteed prediction, accuracy or outperformance. ## Frequently Asked Questions Is Rank Correlation Index a buy or sell signal? No. It ranges from -100 to +100. Using ranks ignores the size of price moves, so a small drift and a large move rank identically. A trade built on it still needs a trigger, an invalidation rule, a position size and realistic execution assumptions. What is the best setting for Rank Correlation Index? Rank Correlation Index takes these inputs: closing prices; window length n (periods such as 9 are used); price rank and time rank within the window. There is no universal best setting for the tunable ones, so test them across instruments, regimes and out-of-sample periods and favor stable parameter regions over one historical winner. Can Rank Correlation Index be used by itself? Using ranks ignores the size of price moves, so a small drift and a large move rank identically. Ties and short windows make the value jump around. For that reason it is read next to measures of direction, participation, valuation, liquidity and risk, not alone. Does Rank Correlation Index work on every timeframe? The calculation (RCI = 100 * (1 - 6 * Sum(d^2) / (n * (n^2 - 1))), where d is the difference between the price rank and the time rank) can be run on any bar size, but behavior is not portable: a reading on a five-minute chart describes a very different market window from the same reading on a daily chart. Validate the exact timeframe before relying on it. Why does Rank Correlation Index give false signals? Time ranks are a fixed sequence, so the value measures only how closely price order follows time order, with no link to volatility or volume. The value moves in discrete steps set by the window length, so a short window offers only a coarse set of possible readings. Lag, noise and regime changes add to this, because market participants react to new information after the reading is calculated. How should Rank Correlation Index be backtested? Rebuild Rank Correlation Index from closing prices using point-in-time data, write the rules before testing, include delisted securities where relevant, model realistic fills and costs, reserve a validation sample and compare with a simpler baseline. S Swoopr Editorial Team The Swoopr Editorial Team produces independent investment education, research, and tools for understanding markets, evaluating opportunities, and managing risk. All content is educational only and does not constitute personalized investment advice. See our [editorial policy](https://www.getswoopr.com/legal/editorial-policy/) and [corrections policy](https://www.getswoopr.com/legal/corrections-policy/).