A triangle on a chart forms when the price keeps testing a range while its highs and lows move closer together. An ascending triangle has a flat top and rising lows. A descending triangle has a flat bottom and falling highs. Both show the same thing from opposite sides: the price is being squeezed into a narrowing range, and a breakout is often expected once the range becomes tight.
This guide explains how to recognise each triangle, why the direction of the breakout matters more than the shape alone, and how a common textbook target is measured. The example uses invented prices. It covers the simple triangles in detail and mentions the symmetrical version only briefly, because that one has no built-in bias. As with all chart patterns, the reading depends on the judgement of the person drawing the lines.
What makes an ascending triangle?
An ascending triangle has a flat upper line, which marks resistance where sellers have repeatedly stopped the price, and a rising lower line, where buyers have stepped in at higher prices each time. The textbook bias is bullish, because buyers are willing to pay more while sellers keep defending the same level.
To draw the shape, connect the highs with a horizontal line and the lows with a rising trendline. Two touches on each line is the minimum many traders use, and more touches make the boundary more meaningful. The triangle should narrow over time, with the range between the lines shrinking as the pattern develops. Volume often contracts while the price is inside the triangle, which signals that fewer traders are active until the break. The bias is only a bias. A breakout can fail or reverse, and a triangle with a rising lower line can still break down through that line, which is a different outcome from the one the shape suggests.
Triangles also differ in how long they take. Some resolve within a few sessions, while others run for weeks. A longer squeeze does not make the breakout more reliable, though it does give more time for volume and the price structure to show what the market is doing. Judge the pattern by its shape and its tests, not by how long it has lasted.
What makes a descending triangle?
A descending triangle has a flat lower line, which marks support where buyers keep stepping in at the same price, and a falling upper line, where sellers arrive at lower prices each time. The textbook bias is bearish, because sellers grow more aggressive while buyers keep defending the same level.
Draw the flat line through the lows and the falling trendline through the highs. The same checks apply: enough touches, a narrowing range and quieter trading during the squeeze. Descending triangles often form during a downtrend, where they can be read as a pause before the next leg down. The risk is the same in mirror image. A close above the falling upper line can end the bearish reading, particularly if the broader market turns up. A descending triangle that breaks upward can be as informative as one that breaks down, because the direction of the break tells you more than the name of the shape.
How is the break and the target measured?
A breakout is usually confirmed by a close beyond the flat line, not by a single intraday spike. A common textbook target is the height of the triangle at its widest point, added to the breakout level for an ascending triangle or subtracted for a descending one.
The table uses invented prices for an ascending triangle. The flat resistance sits at 50, and the widest part of the triangle is at the start of the pattern, where the low was 40. The height is therefore 10.
| Step | Level | What it means |
|---|---|---|
| Flat resistance (top) | 50 | Sellers held this level several times |
| Widest point (low at the start) | 40 | The first low of the pattern |
| Triangle height (50 − 40) | 10 | Used for the textbook target |
| Breakout close | 50.5 | A close just above the flat line |
| Textbook target (50 + 10) | 60 | A reference for planning, not a guarantee |
| Invalidation (close back below) | 49 | Below this level the breakout has failed |
The target is a projection, not a forecast. Many breakouts stall before the full distance is reached, and the textbook target does not say how long the move will take. In this example, the stop sits just below the flat line, so a failed breakout costs a small and known amount rather than a loss that grows with the target.
Some traders measure the target from the point where the triangle was first drawn, while others use the breakout level alone. Both approaches are conventions. What matters is that you choose one method, write it down and apply it to every triangle, so your results can be compared later.
What makes triangles fail?
Triangles fail when the breakout is a close that reverses back inside the range, when volume does not support the move, or when the wider market moves against it. A breakout that fills within a few days and returns inside the triangle is a common failure, sometimes called a false breakout.
Look for a breakout that happens on a very quiet day with no follow-through on the next session. A breakout that holds a retest of the broken line is more convincing than one that runs straight away and never looks back. Also check the level of the flat line itself. Round numbers, prior highs and moving averages can all act as resistance or support, and they can stop a breakout. Studies of chart patterns report mixed results, and the claims in this guide are general summaries rather than findings from a specific study. The backtest guide linked below explains why a pattern that looks clean in hindsight can perform differently in live trading.
A triangle can also fail slowly. If the range never narrows, or the price keeps touching the flat line without a clean close either way, the pattern has stopped behaving like the textbook shape. In that case the honest answer is that there is no pattern yet, and waiting is a valid decision.
Common mistakes
Calling any converging lines a triangle. The shape needs a flat line and a sloping line, with a clear narrowing range. Lines that wander are not a pattern.
Trading the shape before the break. A triangle is not a signal until the price closes beyond the flat line.
Ignoring the direction of the wider trend. A bullish ascending triangle inside a strong downtrend deserves more caution than one that appears in an uptrend.
Checklist
- Identify the flat line and check that the price touched it at least twice.
- Draw the sloping line through the other turning points and confirm the range is narrowing.
- Note whether volume has contracted during the squeeze, if your data shows it.
- Wait for a close beyond the flat line before you treat the triangle as broken.
- Measure the height of the triangle at its widest point and mark the textbook target.
- Set an invalidation level, such as a close back inside the triangle.
- Compare the setup with the broader trend before you act.
Key takeaways
An ascending triangle has a flat top and rising lows, and a descending triangle has a flat bottom and falling highs. Both are read as a squeeze that often resolves in a breakout, with a bullish bias for the first and a bearish bias for the second. The direction of the actual break, the close and the retest matter more than the name of the shape.
This guide is for general information, not financial advice. See the disclaimer.