Force index
Force index multiplies each day's price change by its volume and smooths the result over 13 bars, measuring whether buyers or sellers currently have both direction and size behind them.
`force_index` is the day's close-to-close price change multiplied by the day's volume, smoothed over 13 bars. The raw product captures a simple idea: a 2% move on heavy volume is a more forceful event than the same move on a quiet tape. Smoothing over 13 bars — Alexander Elder's intermediate setting — turns a jagged daily series into a line whose sign is readable.
The zero line is the whole signal. Force index is negative while sellers have both direction and size, positive when buyers do, and the cross is the event: `force_index crosses above 0` marks the session where price change and volume stopped agreeing on down. Elder designed the cross as a pullback entry inside an uptrend, which is why the Force index turning positive scan pairs it with `close > sma(50)` — the zero cross in a downtrend is just a bounce with arithmetic attached.
Because price change and volume are multiplied, one outsized session dominates the smoothed line for days — a block trade on a down day can hold the index negative through a genuine turn. It is also unbounded and unnormalised, so levels are not comparable across stocks; only the sign and the crosses travel. Against its volume siblings, force index is the tempo instrument: OBV and A/D accumulate history, force index reads the last two or three weeks and forgets the rest.
In Sift
Written as force_index — signed, 13-bar smoothed; zero is the line that matters. A working scan — Price change and volume agreeing the dip is done, inside an uptrend:
where force_index crosses above 0 and close > sma(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 does force index crossing zero mean?
The 13-bar smoothed product of price change and volume has flipped sign. A cross above zero means the recent balance of direction-times-size has shifted to the buyers; below zero, to the sellers. Elder's use for the bullish cross was as a pullback entry in stocks whose larger trend is already up.
What period is the force index calculated over?
Here it is smoothed over 13 bars, Elder's standard intermediate-term setting. He also described a 2-bar version for short-term timing, but the 13-bar form is the one exposed as force_index — smooth enough that its zero crosses are events rather than daily noise.