The Nasdaq drifts down for three days, printing small red candles, tired sellers pushing a market that's basically out of steam. Then one candle opens below the prior close, dips further, and reverses to close not just above that candle's open, but comfortably above the highs of the last two sessions. That's an engulfing candle, and unlike a lot of single-candle shapes, it's actually describing something real: control of the bar changed hands completely, not just at the edges.
What engulfing actually requires
A bullish engulfing candle opens at or below the previous candle's close, then closes above the previous candle's open, its body fully swallowing the prior candle's body (wicks don't count). A bearish engulfing candle does the reverse: opens at or above the prior close, closes below the prior open. The requirement is strict for a reason. A candle that merely closes higher than yesterday isn't engulfing anything; it has to erase the entire prior candle's ground, open to close, inside its own body.
Why the size of the engulf matters
Not all engulfing candles carry equal weight. An engulfing candle that swallows a single small-bodied candle, say a 5 pip EURUSD body from a quiet Asia session, is unremarkable; there wasn't much to overturn. An engulfing candle that swallows two or three candles' worth of range in one move, gold reversing $14 of decline in a single bar after three days of $4 to $5 candles, is a genuine statement about how fast sentiment flipped. Measure the engulf against what it's actually erasing, not just against the pattern's textbook shape.
Context: trend exhaustion beats fresh momentum
An engulfing candle means the most at the end of a stretched move, where the prior trend was already losing steam, smaller bodies, longer wicks, slowing follow-through, before the reversal candle arrives. An engulfing candle appearing in the middle of a strong, healthy trend is often just a normal pullback candle that happens to fit the shape, and treating it as a reversal signal there is how traders fade strong trends straight into a loss. The same holds at a level: an engulfing candle at a well-tested support or resistance zone carries far more weight than the identical shape forming in open space with nothing behind it.
A realistic way to trade it
Wait for the close, always. An engulfing candle isn't confirmed until it actually closes past the prior open, and acting on the intrabar shape before the close is how you get faked out by a wick that recovers. Once closed, the entry sits near that close, and the stop goes beyond the engulfing candle's own extreme, not the prior candle's, because that's the level that would invalidate the whole reversal. On a $10,000 account, a bearish engulfing candle on the Nasdaq with a 45 point stop, at $1 per point per contract, sizes to roughly 2 contracts under the 1% rule. That's a small, deliberate position on a pattern that, even at a real level, still loses a meaningful share of the time.