Double bottom (W) and double top (M): what they are, and how to test them
A double bottom, the W, is two swing lows at about the same price with a swing high between them. It completes when price closes above that high, the neckline. The double top, the M, is the mirror image. Here is the exact rule QuantLogic uses, and how to test both.
What it is
Price falls to a low, bounces, falls back to about the same low, then rises again. Drawn with a line, it looks like a W.
The high between the two lows is the neckline. Until price closes above it, the W is not complete; many never are.
The exact rule QuantLogic uses
W, double bottom (the long side). The M, double top, is the mirror image.
- The last two confirmed swing lows are within 10% of the average daily range (ATR) of each other.
- There is a confirmed swing high between them. The highest one is the neckline.
- This bar closes above the neckline, and the bar before closed at or below it.
When is it known? A swing low is a bar whose low is under the 3 bars before it and not undercut by the 3 after it, so it is only confirmed 3 bars later. The W fires on the close through the neckline, using only swings already confirmed then. The average daily range is the mean of the last 14 regular sessions' ranges, known before the open.
Versions you can build
- W (double bottom) completing. Two equal swing lows, a close above the high between them.
- M (double top) completing. Two equal swing highs, a close below the low between them.
What to look at around it
In QuantLogic, every time the idea happened is laid out with the data points around it, so you can see where it held and where it didn't:
Traps when you test it
- Calling it a W before the neckline breaks. Two equal lows on their own are not the pattern.
- Drawing the second low with hindsight. It is only confirmed 3 bars after it prints.
- Testing only Ws in a rising market. Check the Ms too.
Build it and test it yourself
Open W (double bottom) completing in Build with QuantLogic. See every time it happened on NQ, ES, Gold or Crude since September 2025, check the long and the short side, add your own filters and run the luck test.
Nothing is proven until it holds live. We give no trading signals and no advice, we never hold your money or your accounts, and we never trade for you.
Questions
- How equal do the two lows have to be?
- Within 10% of the market's average daily range of each other, so the tolerance adapts to how much the market moves.
- When does QuantLogic count the pattern?
- On the close of the first bar that closes above the neckline, not when the second low prints.
- Is a completed W a buy signal?
- No. It describes a shape. QuantLogic gives no signals; you test it and decide.
Related setups
Setup library
Liquidity sweeps, break of structure, VWAP, the opening range and more, drawn and explained with the exact rule.
Head and shoulders
Three swing highs, the middle one highest, then a close below the neckline.
Liquidity sweep
Price runs through equal lows or highs, or yesterday's level, then closes back.
Break of structure
A close past the last swing high in an uptrend, or the last swing low in a downtrend.
Change of character
The first close through the last swing against the trend, and the retest after it.
Educational content, not investment advice. Futures trading involves substantial risk of loss. See the risk disclosure.