Harmonic Pattern Calculator
Calculate harmonic pattern ratios for Gartley, Butterfly, Bat, and Crab patterns. Enter values for instant results with step-by-step formulas.
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Where XA is the initial price swing, and each subsequent leg (AB, BC, CD) must align with specific Fibonacci ratios unique to each pattern type. The D point defines the Potential Reversal Zone where price is expected to reverse.
Last reviewed: December 2025
Worked Examples
Example 1: Bullish Gartley Pattern on EUR/USD
Example 2: Bearish Crab Pattern on Gold
Background & Theory
The Harmonic Pattern Calculator applies the following established principles and formulas. Foreign exchange markets facilitate the conversion of one currency into another and serve as the largest and most liquid financial markets in the world, with daily turnover exceeding seven trillion US dollars. Exchange rates are quoted as currency pairs, expressing the price of one unit of a base currency in terms of a quote currency. For example, a EUR/USD rate of 1.0850 means one euro buys 1.0850 US dollars. The smallest standardized price movement in most pairs is the pip, typically the fourth decimal place, with a value of 0.0001 per unit for USD-denominated pairs. The bid price is the rate at which a dealer will buy the base currency, while the ask price is the rate at which it will sell. The spread between bid and ask represents the dealer's compensation and varies with liquidity and volatility. Leverage amplifies both gains and losses by allowing traders to control positions larger than their deposited margin. A 100:1 leverage ratio means a one-percent adverse move eliminates the entire margin, making position sizing and risk management critical. Two parity conditions from international economics anchor exchange rate theory. Purchasing Power Parity (PPP) holds that exchange rates should adjust over time so that identical goods trade at equivalent prices across countries: S = P_d / P_f, where S is the spot rate and P_d and P_f are domestic and foreign price levels. PPP performs well over long horizons but poorly in the short run due to trade barriers, non-tradable goods, and capital flows. Covered Interest Rate Parity (CIRP) is a near-arbitrage condition stating that forward exchange rate premiums or discounts exactly offset interest rate differentials between two currencies: F/S = (1 + r_d) / (1 + r_f). Deviations from CIRP create riskless arbitrage opportunities that traders rapidly eliminate. Uncovered Interest Rate Parity posits that high-yielding currencies should depreciate to offset their interest advantage, though empirical evidence is mixed and the carry trade — borrowing in low-rate currencies to invest in high-rate ones — has generated persistent returns.
History
The history behind the Harmonic Pattern Calculator traces back through the following developments. For much of the nineteenth century and early twentieth century, the international monetary system operated under the classical gold standard, under which each participating currency was fixed to a defined weight of gold, making bilateral exchange rates effectively constant. The system provided price stability and facilitated global trade but constrained governments' ability to respond to economic downturns. World War One shattered the gold standard as nations suspended convertibility to finance wartime expenditures. The interwar period saw attempts to restore gold convertibility, most notably the British return to the gold standard in 1925 at the pre-war parity, a decision criticized by John Maynard Keynes as deflationary. The Great Depression forced widespread currency devaluations and the effective collapse of the international gold standard by the early 1930s. The Bretton Woods Conference of July 1944 established a new order in which member currencies were pegged to the US dollar, while the dollar alone was convertible into gold at 35 dollars per troy ounce. The International Monetary Fund and World Bank were created at the same conference to oversee the system. Bretton Woods delivered exchange rate stability during the postwar growth era but came under strain as US deficits and European dollar accumulation outpaced American gold reserves. On August 15, 1971, President Nixon announced the suspension of dollar-gold convertibility — the so-called Nixon Shock — effectively ending the Bretton Woods system. By 1973, major currencies had transitioned to floating exchange rates determined by market supply and demand, a regime that has persisted. On September 16, 1992, hedge fund manager George Soros shorted the British pound against the European Exchange Rate Mechanism constraints, forcing the UK's withdrawal in what became known as Black Wednesday. Electronic trading platforms emerged in the 1990s and 2000s, replacing voice-brokered interbank markets and dramatically reducing transaction costs for institutional and retail participants alike.
Frequently Asked Questions
Formula
D = A + (XA x Fibonacci Ratio) | PRZ = Cluster of Fibonacci completions
Where XA is the initial price swing, and each subsequent leg (AB, BC, CD) must align with specific Fibonacci ratios unique to each pattern type. The D point defines the Potential Reversal Zone where price is expected to reverse.
Worked Examples
Example 1: Bullish Gartley Pattern on EUR/USD
Problem: Identify a bullish Gartley pattern with XA leg of 150 pips starting from price 1.1000. Calculate the key Fibonacci levels for points B, C, D and the PRZ.
Solution: XA leg = 150 pips from 1.1000 to 1.0850 (bearish XA for bullish pattern)\nAB = 61.8% of XA = 150 x 0.618 = 92.7 pips up from A = 1.0943\nBC = 61.8% of AB = 92.7 x 0.618 = 57.3 pips down = 1.0886\nCD = 127.2% of BC = 57.3 x 1.272 = 72.9 pips up\nD point (PRZ) = 78.6% retracement of XA = 150 x 0.786 = 117.9 pips = 1.0968
Result: PRZ at 1.0968 | Stop Loss below 1.0840 | TP1 at 1.1000 | TP2 at 1.1040 | Risk:Reward = 1:2.5
Example 2: Bearish Crab Pattern on Gold
Problem: Calculate a bearish Crab pattern with XA leg of $50 starting from $1,950. Determine the extended D point and optimal entry/exit levels.
Solution: XA leg = $50 from $1,950 to $2,000 (bullish XA for bearish pattern)\nAB = 50% of XA = $25 down from A = $1,975\nBC = 61.8% of AB = $15.45 up = $1,990\nCD = 261.8% of BC = $40.45 down\nD point = 161.8% extension of XA = $50 x 1.618 = $80.90 = $2,031
Result: PRZ at $2,031 | Stop Loss above $2,040 | TP1 at $2,010 | TP2 at $1,990 | Risk:Reward = 1:2.3
Frequently Asked Questions
What are harmonic patterns in trading and how do they work?
Harmonic patterns are geometric price structures based on Fibonacci ratios that help traders identify potential reversal zones in the market. They were pioneered by H.M. Gartley in 1935 and further developed by Scott Carney and Larry Pesavento. Each pattern consists of specific price swings labeled X, A, B, C, and D, where the ratios between these legs must align with precise Fibonacci numbers. When price reaches the completion point (D), it enters a Potential Reversal Zone where the probability of a trend reversal is statistically higher. Traders use these patterns to find high-probability entries with clearly defined risk-to-reward ratios.
What is the Gartley pattern and what Fibonacci ratios define it?
The Gartley pattern, also known as the Gartley 222, is the original harmonic pattern identified by H.M. Gartley in his 1935 book. In a bullish Gartley, the AB leg retraces 61.8% of the XA leg, the BC leg retraces between 38.2% and 88.6% of the AB leg, and the CD leg extends 127.2% to 161.8% of the BC leg. The critical D point must complete at the 78.6% retracement of the XA leg. This pattern has one of the highest success rates among harmonic patterns because the D point completion zone is relatively shallow, providing better risk-to-reward setups compared to extended patterns like the Crab.
How does the Butterfly pattern differ from the Gartley pattern?
The Butterfly pattern, defined by Bryce Gilmore and refined by Scott Carney, differs from the Gartley primarily in the D point completion level. While the Gartley completes at a 78.6% retracement of XA (within the XA range), the Butterfly extends beyond point X, completing at the 127.2% extension of the XA leg. The AB leg retraces 78.6% of XA (deeper than the Gartley), and the CD leg typically extends 161.8% to 261.8% of the BC leg. Because the D point extends beyond X, Butterfly patterns often signal stronger reversals and are particularly effective at identifying significant market turning points and trend exhaustion zones.
What is the Bat pattern and why is it considered highly reliable?
The Bat pattern, discovered by Scott Carney in 2001, is considered one of the most accurate harmonic patterns due to its precise Fibonacci alignment. The AB leg retraces between 38.2% and 50% of XA, the BC leg retraces 38.2% to 88.6% of AB, and the CD leg extends 161.8% to 261.8% of BC. The D point completes at exactly 88.6% retracement of the XA leg, which is a deep retracement that often coincides with strong support or resistance levels. The tighter AB retracement range (38.2% to 50%) makes the Bat pattern more selective than others, filtering out lower quality setups and resulting in a historically higher win rate when traded with proper confirmation and risk management.
How does the Crab pattern provide extreme reversal opportunities?
The Crab pattern, also identified by Scott Carney, features the deepest D point extension of any standard harmonic pattern, completing at the 161.8% Fibonacci extension of the XA leg. The AB leg retraces 38.2% to 61.8% of XA, the BC leg retraces 38.2% to 88.6% of AB, and the CD leg extends a dramatic 261.8% to 361.8% of BC. This extreme extension means the Crab pattern identifies major turning points where price has been pushed to an unsustainable extreme. While the extended move means a wider stop loss is needed, the subsequent reversal is often equally dramatic, providing exceptional reward-to-risk ratios of 3:1 or better when the pattern validates correctly.
What timeframes work best for harmonic pattern trading?
Harmonic patterns can be traded on any timeframe, but their reliability generally increases on higher timeframes. Patterns on the daily and 4-hour charts tend to produce the most reliable signals because they reflect broader market sentiment and filter out noise. The 1-hour chart offers a good balance between signal frequency and reliability for intraday traders. Patterns on 15-minute and 5-minute charts generate more frequent signals but have lower completion rates and are more susceptible to false breakouts. Many professional harmonic traders use a multi-timeframe approach, identifying patterns on higher timeframes for directional bias and then using lower timeframes to fine-tune entries within the Potential Reversal Zone.
References
Reviewed by Daniel Agrici, Founder & Lead Developer · Editorial policy