Gann fan
A set of lines from one swing point at fixed angles, such as one unit of price for each unit of time.
What it shows
A Gann fan starts at a swing low (or high) and draws lines at fixed ratios of price to time. The key line is 1×1: one unit of price for each unit of time, which is 45 degrees on a chart with equal axes. Others include 2×1, 1×2, 3×1 and 1×3.
The lines are drawn from a rule rather than fitted to the data. They depend on the scale you choose, so a different scale makes a different fan. Many traders treat them as a visual guide only.
How we find it
The same code that draws it on your chart follows these steps, with the same result every time.
- Pick a swing low or swing high as the start.
- Choose a price-per-bar unit for the 1×1 line (for example, the average true range per bar).
- Draw 1×1, 2×1, 1×2, 3×1 and 1×3 lines from the start using multiples of that unit.
- Extend the lines to the right.
Starting values: Unit of price per bar 14-bar average true range; Lines 1×1, 2×1, 1×2, 1×3, 3×1. These are proposed and will be tuned on real price data before launch.
How to read it
- The violet line is the 1×1 line.
- Lines steeper than 1×1 show faster rises. Flatter lines show slower rises.
- Which lines price has stayed above shows its speed.
Status labels you may see
| Label | What it means |
|---|---|
| Above the 1×1 line | The last close is above the 1×1 line. |
| Between 1×1 and 1×2 | Between the two lines. |
| Below 1×2 | Under the 1×2 line. |
What cancels it
A close below the 1×2 line, or below the lowest line drawn.
What traders check next
- Which line price used as support.
- Whether the unit of price per bar is sensible for the stock.
- Whether other tools show similar levels.
Limits
- The lines change with the scale chosen. There is no single right fan.
- Gann's methods are debated and not proven by research.
- Price often ignores the lines.
Try it in forecastviz
- Open any ticker and choose Trendlines and channels → Gann fan in the left menu.
- Switch between 6M, 1Y, 3Y to see how the picture changes.
- Compare with Trendline fan and Speed resistance lines on the same chart.
Questions
Is this scientific?
The lines follow a fixed rule, but there is no strong evidence that price respects them. We show it because many people ask for it.
What does 1×1 mean?
One unit of price for each bar of time.
Related trends
Further reading
- Murphy, Technical Analysis of the Financial Markets
- Edwards and Magee, Technical Analysis of Stock Trends
Educational only. Not financial advice, and not a price forecast. Charts are drawn by code from past price data, which may be delayed.