Force Index explained: Elder volume momentum oscillator
By Ken Chigbo, Founder, KenMacro. Published 2026-05-13.
Quick answer
The Force Index is an oscillator developed by Alexander Elder that multiplies the difference between today’s close and yesterday’s close by the period’s volume. It quantifies the conviction behind price moves, with positive readings signalling buying pressure and negative readings signalling selling pressure. Traders typically apply an exponential moving average to smooth the raw values.
What is force index?
The Force Index is a volume-weighted momentum oscillator introduced by Dr Alexander Elder in his 1993 book Trading for a Living. It is calculated by taking the change in closing price from one period to the next and multiplying that figure by the volume traded during the period. The raw output oscillates around a zero line, with the magnitude reflecting the size of the price move and the participation behind it. Most charting platforms smooth the raw series with a 13-period exponential moving average, producing a cleaner indicator that highlights shifts in directional pressure rather than single-bar noise.
How traders use force index
Retail traders typically watch the Force Index for three signals: zero-line crossovers as a trend filter, divergences between the oscillator and price as early reversal warnings, and short-period spikes as exhaustion or breakout confirmation. A two-period Force Index is often used to time pullback entries within an established trend, while a thirteen-period version tracks the broader pressure regime. Institutional desks rarely cite the Force Index by name, but the underlying logic, price change weighted by participation, mirrors how order-flow analysts assess aggression behind a move. Because the indicator requires reliable volume data, equity and futures traders apply it directly, whereas forex traders substitute tick volume from their broker feed, accepting that this is a proxy rather than true contract volume.
Common misconceptions about the Force Index
The most frequent mistake is treating tick volume in forex as equivalent to the volume used in Elder’s original equities work. Tick volume reflects update frequency, not contracts traded, so readings vary by liquidity provider and session. A second misconception is that large absolute Force Index values are always bullish or bearish; they simply indicate conviction, which can mark either continuation or exhaustion depending on context. Finally, many traders use the raw single-bar output and complain of noise, when Elder explicitly designed the 13-period smoothed version for trend assessment and the 2-period version for entry timing.
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Frequently asked
What is the formula for the Force Index?
The single-period Force Index equals the current close minus the previous close, multiplied by the period’s volume. The result is expressed in the same units as volume, so a $0.50 advance on one million shares produces a reading of 500,000. Elder then applies a 13-period exponential moving average to the raw series to filter noise. A shorter 2-period EMA is used as a sensitive trigger inside an established trend identified by the longer smoothing.
How is the Force Index different from On Balance Volume?
On Balance Volume adds or subtracts the full period volume based only on the direction of the close, ignoring the size of the price change. The Force Index instead scales volume by the actual magnitude of the move, so a one-cent close on heavy volume contributes far less than a one-dollar close on the same volume. This makes the Force Index more responsive to the strength of individual bars, while OBV emphasises cumulative directional participation over longer windows.
Can the Force Index be used in forex trading?
Yes, but with an important caveat. Spot forex has no centralised volume figure, so the indicator relies on tick volume from the trader’s broker. Tick volume correlates reasonably well with actual traded volume during liquid sessions, but it diverges during thin periods and varies between liquidity providers. The desk treats forex Force Index readings as a relative measure of activity rather than an absolute one, and prefers it on majors during the London and New York overlap when feeds are deepest.
What does a Force Index divergence signal?
A bullish divergence occurs when price prints a lower low but the Force Index prints a higher low, suggesting selling pressure is fading even as price extends. A bearish divergence is the mirror image, with price making a higher high while the oscillator makes a lower high. Elder treats these as warnings rather than triggers, recommending that traders wait for additional confirmation such as a zero-line crossover or a price structure break before acting on the signal.
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