Fibonacci Fan Calculator
Project the 38.2%, 50%, and 61.8% diagonal Fibonacci fan trendlines forward from a swing high and low.
Fan Lines
Fan Line Detail
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A Fibonacci fan is a diagonal variant of the Fibonacci Retracement Calculator: instead of flat horizontal support and resistance levels, it draws sloped trendlines fanning out from the swing's start, each one passing through a Fibonacci ratio point plotted on the vertical line at the end of the swing.
Because the lines are sloped rather than flat, the price each one "predicts" changes with time, useful for a market that's trending rather than moving sideways.
How does this calculator work?
Enter the swing low and swing high prices, the trend direction, how many bars (candles) the swing took from start to end, and how many bars past the end of the swing you want to project each fan line forward to.
The calculator first finds where each fan ratio (38.2%, 50%, 61.8%) crosses the vertical line at the end of the swing, using the same math as the Retracement Calculator: for an uptrend, anchor price = swing high − (ratio × range).
It then draws a straight line from the start of the swing (the low, in an uptrend) through that anchor point, and calculates the line's slope: (anchor price − starting price) ÷ swing duration in bars.
Finally, it extends that slope forward to whatever future bar you specify, giving the price each fan line would be at by then: starting price + (slope × total bars from the swing's start). A chart plots all three fan lines alongside the swing itself, so you can see them visually diverging from the same starting point.
Worked example
A stock swings from $50 to $100 over 10 bars (an uptrend), and you want to project each fan line 5 bars past the end of the swing.
- 38.2% fan line at bar 15
- $96.35
- 50% fan line at bar 15
- $87.50
- 61.8% fan line at bar 15
- $78.65
How the numbers work
The 50% anchor point sits at $75 (the midpoint) on the vertical line at bar 10. The line from the $50 starting point through that anchor rises $2.50 per bar (($75 − $50) ÷ 10).
Extended out to bar 15 (5 bars past the swing's end), that same slope puts the 50% fan line at $50 + ($2.50 × 15) = $87.50.
Because each fan line has its own slope, they spread apart the farther forward you project, similar to how three trendlines drawn from the same starting point but through different points fan out visually on a real chart, hence the name.
Fibonacci Fan Calculator glossary
- Fibonacci Fan
- A set of diagonal trendlines drawn from the start of a price swing through Fibonacci ratio points on the vertical line at the end of the swing, then extended forward as sloped support or resistance.
- Anchor Price
- The price where a fan line crosses the vertical line at the end of the swing, calculated the same way as a standard retracement level.
- Slope
- The rate of price change per bar along a fan line, determined by the anchor price, the starting price, and the swing's duration in bars.
Fibonacci Fan Calculator FAQs
How is this different from a regular retracement level?+
A retracement level is a flat horizontal price. A fan line is a diagonal one, so the price it points to keeps changing as time (bars) passes. Fans are typically used in trending markets, where a flat horizontal level doesn't account for the trend's own momentum.
Why only 38.2%, 50%, and 61.8%?+
These three are the fan lines most commonly plotted in practice, the same three most-watched levels from standard retracements. Charting platforms sometimes add 23.6% or 78.6% fan lines too, but 38.2/50/61.8 cover the core use case.
What counts as a "bar"?+
Whatever timeframe you're analyzing, a bar is one candle: one day on a daily chart, one hour on an hourly chart, and so on. The swing duration and projection bars should use the same timeframe consistently.
Do these lines actually get respected by price?+
Like all Fibonacci tools, fan lines are watched by enough traders that they can become somewhat self-fulfilling, but there's no guarantee price respects any specific line. Treat a fan line crossing as an area of interest to combine with other signals, not a standalone trade trigger.
Related Calculators
Fibonacci Retracement Calculator
Find the standard 23.6%, 38.2%, 50%, 61.8%, and 78.6% retracement price levels from a swing high and swing low.
InvestingFibonacci Extension Calculator
Project price targets beyond a swing move using the 127.2%, 161.8%, 200%, and 261.8% extension levels.
InvestingFibonacci Arc Calculator
Find where the 38.2%, 50%, and 61.8% Fibonacci arcs cross at a future bar, based on a swing high and low.