Fibonacci Arcs
Fibonacci arcs are half circles drawn from the end of a price move, with radii of 38.2%, 50% and 61.8% of the move's base line. They mark curved support or resistance zones that combine price and time.
Fibonacci arcs take the familiar retracement ratios and bend them into curves. Instead of a level that stays fixed forever, an arc's support or resistance changes as time passes after the swing. It is a niche tool, but some traders like how it captures both how far and how long a pullback runs. This entry explains how arcs are drawn, read and used.
- Category
- Technical Analysis
- Reading time
- 3 min
- Also called
- Fibonacci arc, Fib arcs
- Updated
Fibonacci arcs in plain words
Fibonacci arcs are half circles that extend from a trend line, set at 38.2%, 50% and 61.8%.1
After an advance, they are measured along a base line from trough to peak and mark possible support or reversal zones on the pullback.1
The same ratios underlie ordinary Fibonacci retracement levels, which traders use to find potential reversal points.2
How to draw Fibonacci arcs, step by step
Choose the move
A significant trough-to-peak swing. See Swing High and Swing Low.
Draw the base line
From the trough to the peak.
Set the radii
38.2%, 50% and 61.8% of the base line.
Draw the arcs
Centred on the peak, curving down and forward.
Watch the pullback
Reactions at arcs show support. See Support and Resistance.
Mirror after declines
Arcs then mark resistance on bounces.
Worked examples
Example 1 — The arc levels
Arcs setAn advance runs from $80 to $120.
| Move | $40 |
| 38.2% arc (at peak date) | $120 − $15.28 = $104.72 |
| 61.8% arc (at peak date) | $120 − $24.72 = $95.28 |
The arcs' radii are 0.382, 0.50 and 0.618 of the base line.1
Example 2 — Support on an arc
+$12The pullback reaches the 50% arc and the stock rebounds from $103 to $115.
| Bounce | $103 |
| Rebound to | $115 |
| Gain | +$12 |
Arcs mark potential support or reversal zones as prices pull back after an advance.1
Example 3 — Resistance after a decline
Bounce failsA stock falls from $60 to $40, then bounces into the 61.8% arc and turns down.
| Decline | $20 |
| Bounce stalls at arc | Resistance |
After a decline, arcs anticipate resistance or reversal zones for the counter-trend bounce.1
Fibonacci arcs vs fans vs time zones
| Aspect | Shape | Adds |
|---|---|---|
| Arcs | Half circles | Price and time together |
| Fans | Diagonal lines | Sloping support. See Fibonacci Fan |
| Time zones | Vertical lines | Timing only. See Fibonacci Time Zones |
| Retracements | Horizontal lines | Price only |
How traders use Fibonacci arcs
Pullback support
Entering at a curved level. See Pullback.
Bounce resistance
Selling rallies in downtrends.
Timing reactions
When price meets an arc, not just where.
Confluence
Combine with horizontal levels. See Fibonacci Retracement and Extension.
Advantages and disadvantages
Advantages
- Combines price and time.
- Uses familiar Fibonacci ratios.
- Levels evolve as time passes.
Disadvantages
- Shape depends on chart scaling.
- Subjective anchor points.
- Less widely watched than retracements.
Going deeper
Read as far as you need. Each level builds on the one before it.
Rounded ratios
Beginner
The first and third arcs use 0.382 and 0.618, often rounded to 38% and 62%, and the middle arc sits at 50%.1
Why scale matters
Intermediate
A circle on a chart depends on how many pixels represent a dollar and a day, so arcs change with zoom and scale settings. See Linear and Logarithmic Scale.
Part of a toolkit
Advanced
Retracement levels are only potential reversal points; arcs add timing but still need confirmation from price.2
Common mistakes
Inconsistent chart scaling
Arcs drift when zoom changes.
Minor swings as anchors
Use significant moves.
Expecting exact touches
Arcs are zones.
Ignoring confirmation
Wait for price to react.
Check your understanding
Test yourself before moving on. Each answer comes with an explanation.
Key points to remember
- Fibonacci arcs are half circles from a swing's end point.
- Radii are 38.2%, 50% and 61.8% of the base line.
- They mark support after advances and resistance after declines.
- They combine price and time.
- Chart scaling changes their shape.
Frequently asked questions
Are Fibonacci arcs popular?
Which ratios do arcs use?
Do arcs work in all markets?
Further learning
- Fibonacci Retracement and Extension
The horizontal levels.
- Fibonacci Fan
Diagonal Fibonacci lines.
- Fibonacci Time Zones
Fibonacci timing.
- Harmonic Patterns
Patterns built on Fibonacci ratios.
Sources
This article is written in our own words. The sources below support the specific facts, rules and figures marked with a number in the text. Links open the original publisher’s page.
- StockCharts ChartSchool. Fibonacci Arcs (opens in a new tab) Checked .
- StockCharts ChartSchool. Fibonacci Retracements (opens in a new tab) Checked .
Educational content, not financial advice. Examples use hypothetical prices and simplified costs; actual fees, margin rules and regulations vary by broker, market and country. We are not affiliated with any publisher linked above. Last reviewed . Report an error or request a source credit.