What Is a Gann Fan?

Michael Whitman · Trading since 2017, full-time since 2020 · YouTube creator, 137K subscribers · Published 2026-09-15 · Updated 2026-09-22

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A Gann fan draws a spray of diagonal lines from one point. It looks like the most precise tool in the family and it rests on the shakiest foundation, for a reason worth understanding before you use one.

How it works

Pick one significant pivot — a major high or low — and the fan radiates from it.

The central line is the 1×1. One unit of price for one unit of time, which in Gann’s framing is the balanced rate at which a market is neither strong nor weak.

The rest are ratios around it — 2×1, 3×1, 1×2, 1×3 — steeper lines above the center, shallower below, each representing a faster or slower rate.

The problem at the center of it

“One unit of price per unit of time” requires you to define both units. How much price is one unit? How much time? Nothing in the data answers that.

So the 1×1 is whatever your chart’s aspect ratio makes it. Stretch the window taller and the angle steepens; widen it and the angle flattens — on identical data.

A Gann box does not have this problem. Its divisions are proportions of a move, so they sit at the same prices however the chart is displayed. The fan’s levels move when the window does.

A worked example

Take a hypothetical market whose bars usually span about 0.50 and occasionally 1.10.

Set the 1×1 at 0.50 of price per bar and the central line rises at roughly the pace of an ordinary bar — which means ordinary movement tracks it and the line tells you very little.

Set it at 1.10, the pace of the wide bars, and the line rises faster than almost every bar, so price falls below it almost immediately and stays there.

Both are defensible choices and they produce opposite readings. The fan has not measured anything; it has drawn the consequence of a unit you picked.

What survives the objection

A single trend line from a pivot is a real observation. Connecting a low to a subsequent low describes a rate the market actually traveled, and that does not depend on scaling.

The fan’s shallower lines act as a fallback ladder. When price breaks one, the next one down becomes the reference, which is a structured way to think about a decaying trend.

And the discipline of one fixed pivot is genuinely useful. Unlike a box, which needs two chosen points, a fan needs one — fewer decisions means fewer ways to fit the past.

So the practical residue is a trend line with a fallback ladder. That is worth something, and it is a smaller claim than the geometry implies — which is the honest way to hold this tool.

The original data

Does any market hold one rate for long? The S&P 500 finished 59% of its ten-day windows higher from 1950 to 2026, yet rose on only 53.1% of individual days.

That mix of up and down days is the constraint on any angled line. A line describing a sustained rate is describing something prices rarely do for long: the path zigzags around it, and a single angle fits the average rather than the ride.

And a fan produces many lines. Each break is a potential decision, each decision costs the spread, and a tool that generates five levels from one pivot generates five times the opportunities to pay it.

Using one without the geometry

Fix your chart settings and never change them. The fan is only internally consistent if the scale it was drawn on is the scale you keep reading it on.

Use a logarithmic scale for long ranges. On a linear scale a fixed angle means a shrinking percentage move as price rises, which makes old fans meaningless on anything that has doubled.

Treat the 1×1 as the only line worth much. The steeper and shallower ratios multiply the clutter without adding independent information.

And accept what the tool is. A fan is a trend line with a scale dependency and a ladder of backups. Used that way it is a reasonable organizing device; used as geometry it is claiming a property the market does not have.

How this connects

Angled lines projected from a pivot, which makes this the sloped cousin of support and resistance and shares its weakness: the pivot is your choice.

The angles assume a fixed price-to-time ratio. Without specifying that ratio the lines are a function of chart scaling rather than of the market.

Trend lines are the simpler version of the same idea - one slope drawn from two points - and they carry the same dependence on which points you pick.

The gann box and gann square come from the same framework, so using them together is one assumption confirming itself.

And a fan covers a lot of chart. Several lines radiating forward will be near whatever price does next, which reads as accuracy and is coverage.

When it fails

The characteristic failure arrives when you change device. A fan drawn on a desktop chart is read later on a phone, where the window is a different shape, and every line now sits somewhere else relative to price. The levels that looked like support are not the levels on the new screen. Nothing about the market changed and nothing about the drawing was wrong — the tool’s output depends on display geometry, which is a property of your screen rather than of the instrument.

A second failure is using a linear scale over a large range, where a fixed angle silently becomes a shrinking percentage.

A third is redrawing from a new pivot whenever the old fan stops fitting, which converts it into a hindsight tool.

A fourth is trading every line. Five angles from one pivot is five ways to pay a spread.

And a fifth is expecting the angles to mean something on their own. An angle is a relationship between two units you chose, not a measurement of the market. Software that draws the fan automatically hides this by picking the units for you, which makes the output look objective while leaving the choice exactly where it always was.

Related

Gann box covers the proportional version that does not depend on scale. Gann square covers the attempt to equate price and time directly. And trend lines covers the simpler tool a fan is built from.

This page is educational, not financial advice. Test every idea on your own charts before risking money. Some links on this page earn a commission if you buy through them. It costs you nothing and it does not decide what appears here or in what order — how these pages are made is set out in our methodology.