--- title: "Decycler: Formula, Meaning & Signals" description: "The Decycler is a John Ehlers trend indicator made by subtracting a high-pass filtered copy of price from price itself. What remains is the part of price..." canonical: https://www.getswoopr.com/indicators/cycle-and-signal-processing/decycler/ source: "Swoopr Investment: https://www.getswoopr.com" --- ## Direct Answer > The Decycler is a John Ehlers trend indicator made by subtracting a high-pass filtered copy of price from price itself. What remains is the part of price with cycles shorter than the cutoff removed, which acts as a low-lag trend line. The line tracks price at trend scale, and price above it means the high-pass component is positive. # Decycler: Formula, Meaning, Signals, Examples and How to Use It ## How Is Decycler Calculated? The Decycler is a John Ehlers trend indicator made by subtracting a high-pass filtered copy of price from price itself. What remains is the part of price with cycles shorter than the cutoff removed, which acts as a low-lag trend line. **Formula:** `Decycler = price - HighPass(price, cutoff period)` **Inputs:** - Close prices - High-pass cutoff period (for example 125 bars) **Worked example.** With a price of 100 and a high-pass output of 2.5, the decycler value is 97.50. The inputs are illustrative numbers, not market data. **Reading it.** The line tracks price at trend scale, and price above it means the high-pass component is positive. Its slope is read as trend direction, and a shorter cutoff makes it hug price more tightly. **Limits.** With a short cutoff it follows price so closely that it adds little information, and with a long cutoff it lags. The first values depend on filter startup. ## What is Decycler? The Decycler is a John Ehlers trend indicator made by subtracting a high-pass filtered copy of price from price itself. What remains is the part of price with cycles shorter than the cutoff removed, which acts as a low-lag trend line. ## How to use Decycler The line tracks price at trend scale, and price above it means the high-pass component is positive. Its slope is read as trend direction, and a shorter cutoff makes it hug price more tightly. A reading alone is never a buy or sell signal; it needs context from price structure, volume, volatility and the broader market regime. ## Strengths - Subtracting the high-pass output from price leaves everything slower than the cutoff, so the trend line is defined by one parameter. - Because price equals decycler plus high-pass, the two outputs are exact complements and nothing is lost between the trend and cyclic parts. - Reproducible when the formula and data convention are fixed. ## Weaknesses and limitations - The cutoff period has to be chosen for each instrument and timeframe, because a value suited to daily bars does not carry over to hourly bars. - It carries no oscillator scale, so the deviation of price from the decycler must be measured separately to judge how stretched price is. - 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 Decycler a buy or sell signal? No. The line tracks price at trend scale, and price above it means the high-pass component is positive. With a short cutoff it follows price so closely that it adds little information, and with a long cutoff it lags. 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 Decycler? Decycler takes these inputs: close prices; high-pass cutoff period (for example 125 bars). 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 Decycler be used by itself? With a short cutoff it follows price so closely that it adds little information, and with a long cutoff it lags. The first values depend on filter startup. For that reason it is read next to measures of direction, participation, valuation, liquidity and risk, not alone. Does Decycler work on every timeframe? The calculation (Decycler = price - HighPass(price, cutoff period)) 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 Decycler give false signals? The cutoff period has to be chosen for each instrument and timeframe, because a value suited to daily bars does not carry over to hourly bars. It carries no oscillator scale, so the deviation of price from the decycler must be measured separately to judge how stretched price is. Lag, noise and regime changes add to this, because market participants react to new information after the reading is calculated. How should Decycler be backtested? Rebuild Decycler from close 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/).