Arc

The Arc tool draws a smooth curved line between two points on the chart. The arc is defined by three points — start, a middle control point, and end — creating a circular or elliptical segment that can be used to trace parabolic price moves, rounded reversals, and curved support and resistance lines. The arc uses quadratic Bezier mathematics to ensure a perfectly smooth, continuous curve at any zoom level or chart resolution.

Arcs are particularly useful for markets that exhibit curved, non-linear price behavior — such as parabolic advances, blow-off tops, and gradual rounding bottoms. Unlike a straight trend line which forces a linear fit onto price action, an arc respects the natural curvature of accelerating or decelerating moves. This makes it indispensable when analyzing assets with strong trending phases that naturally curve as momentum builds and decays over extended timeframes.

The control point is the key to shaping the arc. Placing it further from the chord — the straight line between start and end — creates a tighter, more curved arc. Placing it closer to the chord creates a flatter, wider curve. After placement, you can drag the control point to fine-tune the curvature independently of the start and end positions. The ability to independently adjust curvature and endpoints makes the arc extremely flexible for fitting complex price structures.

Arcs can be styled with or without a fill between the arc and the chord. When using the fill, choose a semi-transparent color (15–25% opacity) so the underlying price bars remain visible. The chord line itself can be shown or hidden independently, giving you full control over the visual footprint. The Lock Aspect feature preserves proportional curvature when you move endpoints, which is useful for maintaining the same visual shape while adjusting the arc's position on the chart.

1. 1
   Select the Arc tool

   Click the Arc icon in the shapes toolbar. The cursor changes to a crosshair for precision placement.
2. 2
   Set the start point

   Click to place the first point at the beginning of the curved move on the chart.
3. 3
   Set the control point

   Click at the peak or trough of the arc to control curvature. The distance from the chord determines the arc height.
4. 4
   Set the end point

   Click at the end of the arc segment. The arc renders immediately connecting all three points smoothly.
5. 5
   Adjust the curvature

   Drag the control point to fine-tune the arc shape. Drag endpoints to reposition the start and end of the arc independently.
6. 6
   Style the arc

   Adjust border color, width, style, and fill settings from the configuration panel.

• Parabolic price moves — trace accelerating advances where price curves upward exponentially. The arc highlights the increasing slope that often precedes a blow-off top. Bitcoin and highly speculative assets frequently exhibit this behavior on weekly charts.
• Rounded reversals — highlight rounding bottoms (saucer bottoms) and rounded tops where price changes direction gradually rather than with a sharp V-reversal. Common in large-cap equities and FX pairs on weekly timeframes where institutional accumulation/distribution takes time.
• Curved support and resistance — draw non-linear boundaries for markets with curved price action. Forex pairs on weekly charts often exhibit curved support and resistance that straight trend lines cannot capture accurately.
• Curve fitting for projections — overlay an arc on a completed parabolic move to estimate where the return-to-mean may end. The arc's symmetry provides a visual target zone at the opposite side of the curve for placing profit targets.
• Educational annotation — mark the curved trajectory of a blow-off top or spike-and-channel pattern in presentations and trading journals. The arc clearly communicates the non-linear nature of the move to viewers.
• Fibonacci arc approximation — manually approximate Fibonacci arcs by placing the control point at a Fibonacci ratio of the chord height (e.g. 0.382, 0.500, 0.618). This bridges the gap between a manual arc and formal Fibonacci arc studies available in advanced charting packages.
• Sine wave fitting — use arcs to approximate half-cycle sine waves in cyclic market analysis. Combine two arcs (upward and downward) to model a complete cycle between two extremes, which is useful for cyclic analysis of commodity and currency markets.

The curvature of an arc is determined by the distance of the control point from the chord — the straight line connecting the start and end points. This distance is known as the sagitta. A larger sagitta creates a tighter curve; a smaller one creates a flatter arc. The exact mathematical relationship is sagitta = r − sqrt(r² − (c/2)²) for circular arcs, where r is the radius and c is the chord length. The sagitta is the single most important parameter for controlling arc shape.

For practical charting purposes, the exact sagitta value matters less than the visual alignment with price action. The goal is to adjust the control point until the arc closely follows the price contour without forcing it. A good rule of thumb: if the arc cuts through the body of too many candles, the control point needs adjustment. The arc should skim the extremes — wicks and closes — not bisect them arbitrarily or cut through the middle of candle bodies.

The fill between the arc and the chord converts the arc from a simple line into a shaded zone that draws attention to the area under the curve. Use this to emphasize the area within a parabolic move or the space between a curved resistance and the baseline chord. The fill creates visual mass that makes the arc section of the chart stand out from unannotated areas.

For best results, match the fill color to the arc color but reduce the opacity significantly to 10–20%. The fill should be a subtle hint of color, not a dominant block that obscures price action. On dark chart themes, blue or purple fills work well. On light themes, light green or orange fills are effective. Avoid using the arc fill on charts that already have significant indicator overlay.

• 1.Arc drawing tool — TradingView Help
• 2.Technical Analysis of Financial Markets — John J. Murphy
• 3.The Geometry of Markets — Gann / financial geometry literature
• 4.The Visual Analysis of Financial Markets — John F. Ehlers
• 5.Cybernetic Analysis for Stocks and Futures — John F. Ehlers
• 6.Parabolic Trading Strategies — Technical analysis reference