EMA (Exponential Moving Average)
The exponential moving average is a moving average that weights recent closes more heavily than old ones, so it tracks a turn in price sooner than a simple average of the same period.
The EMA applies an exponential decay to the closes: each new bar gets a fixed fraction of the weight, and every older bar's influence shrinks geometrically. The practical effect is that a 21-day EMA responds to this week's prices far more than to prices from a month ago, where a 21-day SMA treats them identically. PatternsRadar seeds each EMA from the SMA of its period, which is the textbook initialisation and keeps early values honest.
On daily NSE bars the common setup is a pair: the 9 or 21-day EMA as the fast line a swing trader wants price to hold, and the 50 or 200-day as the slow regime filter behind it. Pullback buyers screen for price returning to a rising 21-day EMA inside an uptrend; trend followers ask whether price has held above the 50 for weeks rather than days, which is a question about persistence, not position.
The cost of responsiveness is false starts. Because the EMA turns with recent price, it also turns with recent noise — in a rangebound stock a short EMA is crossed constantly, and each cross looks like the last one that worked. The lag is reduced, never removed: an EMA is still an average of the past, and no weighting scheme makes an average predictive.
Against the SMA, the choice is a trade of smoothness for speed. The two 200-day lines rarely disagree by much; the two 9-day lines disagree constantly, and that is where the choice matters. Traders who act on short-period crosses tend to prefer the EMA precisely because it front-loads the recent evidence — which is also why it generates more signals to be wrong about.
In Sift
Written as ema(21) — precomputed at 9, 21, 50, 200. A working scan — stocks holding above a 21-day EMA that itself sits above the 50 — an uptrend at two speeds:
where close > ema(21) and ema(21) > ema(50)1
of the 500 most-traded NSE stocks match today, as of 20 Aug 2026
Scans that use it
Prebuilt scans in the library whose query reads this value — each with a hit-rate replay over the last 250 sessions.
Common questions
What period EMA should I use?
It depends on the holding period you are timing. The 9 and 21-day EMAs are swing-trading lines — price should hold them in a strong trend. The 50-day is the intermediate filter, the 200-day the long-term regime. Shorter is faster and noisier; there is no free responsiveness. The replay on each scan page lets you compare periods on actual history rather than folklore.
Why does the EMA react faster than the SMA?
Because of how it distributes weight. The SMA gives every bar in its window an equal vote; the EMA gives the newest bar the largest vote and shrinks each older bar's geometrically. When price turns, the newest bars carry the news, so the EMA bends first. The same property makes it more responsive to noise as well as to signal.