What is Fibonacci Retracement?
Fibonacci Retracement is a charting method that draws horizontal levels at specific percentages of the distance between two selected points on a price chart. The two points are usually described as a swing high and a swing low, or vice versa, depending on the direction you are measuring.
The key point is that the Fibonacci part is mathematical: it uses fixed ratios (commonly 23.6%, 38.2%, 50%, 61.8%, and 78.6%). What changes from chart to chart is the selection of the two anchor points (the high and low), which makes the resulting levels variable even though the ratios do not.
How does a worked example work?
A worked example requires explicit assumptions so the calculations can be verified.
Assumptions for the example below:
- We are measuring from a swing high to a swing low in a way that fits the standard “retracement from high” convention.
- We use the common Fibonacci ratios 23.6%, 38.2%, 50%, and 61.8% (78.6% is optional; it follows the same idea).
- We ignore real-time data changes and treat prices as fixed numbers for the calculation.
- We assume “retrace level” means: a percentage of the high-to-low range added to the low (for the high-to-low measuring direction).
Worked example (numerical):
- Assume swing high = 1.2000
- Assume swing low = 1.1000
- Range = high − low = 1.2000 − 1.1000 = 0.1000
Now compute each retracement level measured upward from the low:
- 23.6% level = low + (0.236 × range) = 1.1000 + (0.236 × 0.1000) = 1.1236
- 38.2% level = low + (0.382 × range) = 1.1000 + (0.382 × 0.1000) = 1.1382
- 50% level = low + (0.500 × range) = 1.1000 + (0.500 × 0.1000) = 1.1500
- 61.8% level = low + (0.618 × range) = 1.1000 + (0.618 × 0.1000) = 1.1618
Verification note: If you re-calculate using the same high, low, and ratios, you should arrive at the same level numbers. That is the “worked example” value: it makes the math checkable without claiming anything about future price behavior.
Evidence-by-calculation vs market behavior (important limitations and failure modes)
A Fibonacci Retracement calculation is deterministic given the inputs, but interpreting its effect on future movement is uncertain.
Material limitations / failure modes to account for:
- Anchor-point selection changes everything. If a different swing high or swing low is chosen, the range changes, and therefore all Fibonacci levels shift. Two people can draw different retracement levels on the same market due to different anchor decisions.
- Past structure does not force future outcomes. Even if price previously paused near a Fibonacci level, that does not establish that it will do so again under new conditions.
- “Levels” are not guarantees. Retracement levels are descriptive lines on a chart, not automatic triggers. Real-world behavior depends on many factors outside the calculation.
- Execution frictions can affect outcomes. Even without assuming any specific broker or platform, slippage, bid/ask spread, and timing differences mean that any real interaction with a level may not match the idealized chart line.
How can you independently verify what you understand next?
To verify your understanding, repeat the worked example with different assumed inputs and check each step:
- Choose two numbers as your swing high and swing low.
- Compute the range as high − low.
- Add low + (ratio × range) for the same measuring direction.
- Confirm that your computed levels are consistent with the ratios you used.
Next question to clarify for yourself: are you measuring from high to low using the “retracement added to the low” convention (as done above), or using the opposite convention? Different tools and drawing preferences can flip the arithmetic direction, which changes where levels land.
If you want, share your chosen swing high and swing low (just the numbers). You can then compute the 23.6%, 38.2%, 50%, and 61.8% levels and confirm they match your charting tool’s output under the same assumptions.