Force Index

The Force Index multiplies the change in close from the prior bar by the current bar's volume, smoothing the product with an exponential moving average into an oscillator around zero that fuses direction, extent, and participation. The multiplication is the point: a strong advance on heavy turnover prints large positive values while a thin drift barely registers.

This build is the standard published formula without modification, defaulting to Alexander Elder's intermediate-term setting of a 13-period EMA. The line draws in a separate pane against a dashed zero line, formatted in volume units.

How to Trade the Force Index?

• Above zero: buyers have had the upper hand — a long-friendly backdrop.
• Below zero: bears control the tape; rallies against sustained negative readings deserve skepticism.
• Zero-line crosses: control has changed hands; bullish and bearish zero-cross alert conditions are included.
• Bullish divergence: price at a lower low while the Force Index bottoms higher shows selling force fading; bearish mirror at highs.
• Extreme spikes: readings far outside recent history mark a surge of one-sided pressure — confirmation with a breakout, or exhaustion after a long run.

Elder gave the lengths different jobs: 13 tracks the swing-scale contest; 2 is a fast pullback timer, buying brief negative readings in an uptrend. Either way, direction comes from a separate trend read — the Force Index times and confirms.

Force Index Settings

• Length (default 13): the EMA applied to the raw one-bar force, (close - close[1]) * volume. Elder used 13 for the intermediate trend and 2 for short-term timing. Raising it favors the slower read; toward 2 the values run nearly raw and whipsaw badly without a trend filter.

Frequently Asked Questions

How does the Force Index differ from On-Balance Volume?

OBV commits each bar's entire volume by the close's direction, so a one-tick up day and a limit-up day count the same. The Force Index weights volume by the size of the price change and is smoothed rather than accumulated, so it distinguishes forceful moves from marginal ones.

Should I use a 2-period or 13-period Force Index?

They answer different questions. The 13-period default gauges which side controls the intermediate trend and supports divergence work; the 2-period variant is an entry timer, flagging brief lulls in pressure for pullbacks within an established trend — deliberately noisy, so direction comes first.

What are the Force Index's limitations?

One outsized bar — a big move on huge volume — can tilt the EMA for a long stretch; smoothing softens but cannot fully remove it. It also inherits its volume feed's weaknesses, so readings deserve less trust where volume is a proxy or fragmented.