The Average Directional Index (ADX) answers a question most indicators skip: is there actually a trend? Moving averages, Supertrend and MACD all assume a trend and tell you its direction. In a sideways market they flip back and forth and give one losing signal after another. ADX, created by J. Welles Wilder, measures how strong the current trend is on a scale from 0 to 100, without saying whether it is up or down. Used alongside its two companion lines, it tells you both.
The three lines: ADX, +DI and −DI
ADX comes as a set of three lines, usually over 14 bars:
- +DI (positive directional indicator) measures how strong the up-moves have been. Each bar, the "up-move" is how much today's high exceeds yesterday's high.
- −DI (negative directional indicator) measures how strong the down-moves have been: how much today's low is below yesterday's low.
- ADX is a smoothed average of the gap between +DI and −DI. When one side dominates for many bars, ADX rises. When they keep swapping, ADX falls.
Both +DI and −DI are divided by the ATR, so they are measured relative to normal volatility. That is why ADX can be compared between a quiet stock and a jumpy one.
DX = |+DI − (−DI)| ÷ (+DI + −DI) × 100; ADX = a 14-bar smoothed average of DX
Reading the numbers
Traders use rough bands. They are conventions, not laws:
| ADX | Common reading |
|---|---|
| Below 20 | Weak or no trend: the price is moving sideways or choppily |
| 20 to 25 | A trend may be starting; watch for confirmation |
| 25 to 40 | A clear trend |
| Above 40 | A very strong trend, sometimes overextended |
Direction comes from the DI lines. ADX at 30 with +DI at 32 and −DI at 12 is a strong uptrend. ADX at 30 with −DI at 35 and +DI at 10 is a strong downtrend. The same ADX number describes both. That is why ADX is almost always read together with the DI lines or with a direction indicator such as a moving average.
A worked example
Imagine a bank stock at ₹780 that has drifted between ₹760 and ₹800 for a month. Its ADX is 14, +DI is 19, −DI is 17: no trend, and the two sides are balanced. Then it closes at ₹812 on strong volume and keeps rising over the next two weeks to ₹860. The up-moves dominate: +DI climbs to 30, −DI drops to 11, and ADX rises from 14 to 27.
A trend follower would read this as a range turning into a trend: ADX crossing above 25 with +DI on top. A range trader who had been selling near ₹800 would read the same numbers as a reason to stop. If the stock then stalls near ₹860 and ADX turns down from 38 while still high, the trend is losing strength, though not necessarily reversing. A falling ADX often means the price is starting to move sideways again.
Comparing trend signals on a live stock
ADX is most useful next to the direction indicators it qualifies. Here are today's readings for Tata Consultancy Services:
The box shows direction signals: price against the 50-day and 200-day averages, MACD against its signal, and Supertrend. If they all agree, the stock probably has a trend and ADX on the technicals page is likely to be above 20. If they disagree (price above the 50-day but below the 200-day, Supertrend flipping), ADX is likely low and those direction signals deserve less trust.
How traders use ADX
- As a filter for trend systems. Take moving-average or Supertrend signals only when ADX is above 20 or 25. This cuts many whipsaw trades in sideways markets, at the cost of entering trends a little late. The F&O bullish trend scan uses exactly this kind of filter.
- As a switch between methods. When ADX is low, oscillators like RSI and the stochastic work better because prices swing between levels. When ADX is high, those oscillators stay "overbought" for weeks and selling on them is costly.
- DI crossovers. +DI crossing above −DI is a buy signal in Wilder's original method, ideally with ADX rising. These crossovers are frequent and noisy on their own.
- Finding strong trends. The strong trend scan lists stocks with ADX above 25 and +DI above −DI, and the screener lets you set your own ADX and DI filters.
Reading the shape of the ADX line
The direction ADX is moving often says more than its level. Four common patterns:
- ADX rising from below 20: a new trend may be forming after a quiet period. This is the moment trend followers watch most closely, because the move is young.
- ADX high and still rising: the trend is strong and accelerating. Pullbacks tend to be shallow and short.
- ADX high but turning down: the trend is slowing. The price may still drift in the same direction, but more slowly and with more overlap between bars. Many traders tighten stops here rather than exit.
- ADX low and flat: a range. Breakout attempts often fail until ADX starts to lift.
A useful habit is to note where ADX turned up at the start of past trends in the stock you trade. Some stocks trend smoothly and ADX climbs above 30 often; others rarely get past 25 even in clear moves. Knowing what is normal for that stock is more useful than a textbook threshold. The ADX line also lags the DI lines: the DI lines usually cross first, and ADX confirms the trend several bars later.
ADX on indices and for option traders
On NIFTY or BANKNIFTY daily charts, a low ADX often goes with a range-bound index, where option sellers tend to do well because the price keeps returning to the middle. A rising ADX warns that a directional move is under way, which is when short straddles and strangles get into trouble. ADX does not replace looking at the straddle or India VIX, but it adds a view of how the index has actually been behaving.
Limits and common mistakes
- Reading ADX as direction. A rising ADX in a falling market means the fall is getting stronger.
- Expecting early signals. ADX is a double-smoothed indicator. It confirms trends after they are already visible on the chart; it is late by design.
- Selling because ADX is high. A high ADX shows strength, not exhaustion. Trends can stay strong for a long time.
- Using a fixed threshold everywhere. 25 is a convention. Some stocks rarely reach it; test the level for what you trade.
- Short timeframes. On 1 or 5-minute charts ADX swings fast and gives many false readings around the open at 09:15.