Harmonic Patterns: Gartley, Bat and Crab Explained
Harmonic patterns are five-point price structures whose legs must sit at specific Fibonacci ratios of one another. If a swing sequence meets the ratio rules, the pattern marks a zone where the move is expected to reverse.
The three best known are the Gartley, the Bat and the Crab. All share the same XABCD skeleton and differ only in the ratios each leg must respect. Get the ratios wrong and it is not the pattern.
Before anything else, be clear on this: harmonic trading is discretionary. Practitioners disagree on tolerances, and the patterns are easy to find in hindsight. Treat what follows as a framework some traders use, not a validated edge.
The XABCD structure
Every harmonic pattern is built from four price legs joining five pivots.
- XA is the impulse leg, the initial move you measure everything against.
- AB retraces part of XA.
- BC retraces part of AB.
- CD is the final leg, and D is where the pattern completes.
The zone around D is called the potential reversal zone, or PRZ. It is a zone rather than a line because the different ratio projections that define D rarely land on the same price. Where the projections cluster, you get the PRZ.
The ratios for each pattern
These are the classical numbers. Tolerances vary between practitioners, and that variation is itself a warning.
| Pattern | B retracement of XA | BC of AB | D point |
|---|---|---|---|
| Gartley | 0.618 | 0.382 to 0.886 | 0.786 retracement of XA |
| Bat | 0.382 to 0.500 | 0.382 to 0.886 | 0.886 retracement of XA |
| Crab | 0.382 to 0.618 | 0.382 to 0.886 | 1.618 extension of XA |
The key distinction is that in the Gartley and Bat, D sits inside the XA leg, so the pattern is a deep retracement. In the Crab, D sits beyond X at the 1.618 extension, outside the original range, which makes it the most extended of the three and the one with the widest reversal zone.
An illustrative Nifty example
Illustrative numbers, not current levels. Suppose X is 23,000 and A is 24,000, so XA is 1,000 points. For a Gartley, B sits near 24,000 minus 618, or 23,382. C then forms back toward A, and D completes near the 0.786 retracement, 24,000 minus 786, or 23,214.
For a Bat with the same XA, B is shallower at 23,500 to 23,618 and D is deeper, near the 0.886 level at 23,114. For a Crab, D projects to 24,000 minus 1,618, or 22,382. Same starting swing, three completion zones over 800 points apart.
How traders use the PRZ
The usual method is to wait for price to enter the PRZ, then look for confirmation from outside the pattern, such as a reversal candle, an RSI divergence, or a break of a short-term trendline. Invalidation sits just beyond the far edge of the zone, which for a Crab means beyond the 1.618 projection.
Position sizing follows from that distance. If a Bank Nifty PRZ spans 250 points and invalidation sits 120 points past it, real risk per unit is close to 370 points, not the tidy number the drawing suggests.
Be honest about the limitations
Three problems deserve stating plainly.
First, hindsight fitting. Once you allow a range for B, a range for C and a tolerance on D, a large share of ordinary five-swing sequences can be labelled as some harmonic pattern. Scrolling back through a Nifty 50 chart and finding examples proves very little.
Second, no standard tolerance. One practitioner accepts a B point at 0.618 plus or minus 0.02, another accepts plus or minus 0.05, and both call the result a Gartley. There is no exchange definition here, unlike a contract size or a settlement rule.
Third, thin evidence. Independently replicated tests of harmonic patterns on Indian equities are scarce. The patterns can still organise where you look for a turn, but do not size positions as though the ratios carry statistical weight.
Frequently Asked Questions
Do I need special software to find these patterns?
Most charting platforms include an XABCD drawing tool that prints the ratios as you place the points, and many offer automatic scanners. Scanners will return far more candidates than are worth looking at, so treat their output as a starting list.
Which harmonic pattern is most reliable?
No credible answer exists, because reliability depends on the tolerances used and the sample tested. The Bat and Gartley complete inside the prior swing, so their invalidation levels are closer, which makes risk easier to control than with a Crab.
How is this different from ordinary Fibonacci retracement?
A retracement measures one leg. A harmonic pattern requires several legs to satisfy ratios at the same time, which is a stricter condition. The extra structure is the whole claim, and also the reason patterns are rare when rules are applied strictly.
Can harmonic patterns be used on options positions?
Traders sometimes use a PRZ to pick strikes, but the pattern says nothing about timing, and options lose value as expiry approaches. A reversal that arrives two weeks late can still lose money on a weekly contract.
Key Takeaways
- Harmonic patterns are XABCD structures where each leg must meet a Fibonacci ratio condition.
- Gartley completes at the 0.786 retracement of XA, Bat at 0.886, and Crab at the 1.618 extension beyond X.
- The PRZ is a zone, not a price, and your real risk spans the whole zone plus the invalidation buffer.
- Tolerances differ between practitioners, so two traders can disagree on whether a pattern exists.
- The patterns are easy to fit after the fact, so treat them as a framework rather than a proven edge.
