Force index

The force index (FI) is an indicator used in technical analysis to illustrate how strong the actual buying or selling pressure is. High positive values mean there is a strong rising trend, and low values signify a strong downward trend.

The FI is calculated by multiplying the difference between the last and previous closing prices by the volume of the commodity, yielding a momentum scaled by the volume. The strength of the force is determined by a larger price change or by a larger volume.^[1]

The FI was created by Alexander Elder.^{[2] [3]}

The force index is commonly calculated by subtracting the previous closing price from the current closing price and multiplying the result by the current period's volume:^[4]

${\displaystyle {\text{Force Index}}=({\text{Current close}}-{\text{Previous close}})\times {\text{Volume}}}${\displaystyle {\text{Force Index}}=({\text{Current close}}-{\text{Previous close}})\times {\text{Volume}}}

For periods longer than one day, the force index is commonly calculated as an exponential moving average of the one-period force index. A 13-period force index, for example, is calculated as a 13-period exponential moving average of the one-period values.^[5]

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