The Commodity Channel Index measures how far price has strayed from its average. Here's how to read the ±100 lines, spot divergence, and which school you're in.

What is the CCI?

The Commodity Channel Index measures one thing: how far the current price has strayed from its own recent average. Donald Lambert designed it for commodities in 1980, hence the name, but it is used on forex, indices and shares without a second thought. When price is unusually far above its mean the CCI runs high; unusually far below, it runs low; and near the mean it hovers around zero.

What it measures

The CCI compares the typical price — high, low and close averaged — against a moving average of that typical price, then scales the gap by how much price has been moving lately. A constant of 0.015 is baked in so that, most of the time, the reading falls between −100 and +100. Step outside that band and price is doing something out of the ordinary for the period you are watching.

You do not need the arithmetic to use it. You need to know that the CCI is a deviation meter: near zero is business as usual, and the further it travels, the more stretched price has become.

Overbought and oversold

The ±100 lines are the ones that matter.

Above +100 — price is stretched to the upside.
Below −100 — price is stretched to the downside.
Between −100 and +100 — ordinary range.

Here the tool splits into two camps. The mean-reversion camp fades the extremes: above +100 they look to sell, expecting price to snap back. The momentum camp does the opposite: a push beyond +100 is a sign of strength, and they trade with it until it fades back through the line. Neither is wrong. But you must decide which one you are, because the same reading is a sell signal to one and a buy signal to the other.

The band that holds "most of the time" does not hold in a strong trend. A trending pair can sit above +100 for days, so fading every +100 in a real trend is a fast way to lose money. The context around the line matters more than the line.

Divergence

The CCI's steadier use is divergence — where price and the indicator disagree. If price makes a fresh high but the CCI makes a lower high, the move up has less force behind it than the last one: bearish divergence. If price makes a new low while the CCI makes a higher low, the selling is tiring: bullish divergence. Divergence does not time anything on its own, but it is an early warning that momentum is draining out of a move.

A worked example

An EA on a £4,000 account uses CCI divergence as a filter. GBP/JPY grinds to a new high, but the CCI prints a lower high — momentum is fading. The EA tightens its long and exits into the stall with about £110 banked, then stands aside rather than chasing the next push. A pure breakout system would have bought that high and given much of it back. The divergence did not predict a crash; it flagged a tiring move and got the EA out of the way.

The catch

The CCI is unbounded — it can reach +300 or −250 — so "overbought" has no ceiling. In a range it reverts nicely and fading works; in a trend it pins to one side and fading is punished. Match the reading to the market you are actually in before you act on any single number.

The Karnek note

Karnek does not calculate the CCI or read its divergences — your EA does that in the terminal. It shows you, read-only, whether a CCI-based strategy is genuinely profitable on your live account over months, not one tidy example. It reads the terminal and can never place a trade.

See it in Karnek: monitor your strategy live with Karnek.