Money Flow Index (MFI)

What Is the Money Flow Index?

The Money Flow Index (MFI) is a momentum oscillator that incorporates both price and volume into its calculation, distinguishing it from purely price-based oscillators like RSI. Developed by Gene Quong and Avrum Soudack, MFI is frequently called the "volume-weighted RSI" because it oscillates on a 0-to-100 scale and uses similar overbought/oversold thresholds, but adds volume data to produce a richer signal.

The calculation begins with the typical price (the average of high, low, and close), multiplied by volume to determine raw money flow. Positive money flow occurs when the typical price is higher than the previous period's typical price; negative money flow occurs when it is lower. The MFI ratio and final formula mirror the RSI structure but use money flow instead of price changes.

How Traders Use MFI

Overbought and oversold signals are the most direct application. MFI above 80 suggests overbought conditions; below 20 suggests oversold. Because MFI factors in volume, these signals can be more meaningful than RSI alone. An overbought MFI reading implies not just that price has risen significantly, but that heavy volume accompanied the rise, potentially exhausting buying demand.

Divergence analysis with MFI carries particular weight because of the volume component. When price makes a new high but MFI fails to confirm with a new high, it means the recent advance lacks volume support. This type of divergence often precedes corrections because it reveals that fewer market participants are driving the most recent leg higher.

Failure swings, similar to those in RSI analysis, provide momentum signals. A bullish failure swing occurs when MFI drops below 20, recovers above 20, holds above 20 on a pullback, and then breaks its prior high. This pattern suggests building buying pressure and often leads to sustained price advances.

MFI vs. Other Volume Indicators

MFI offers advantages over simpler volume indicators because it combines price position, direction, and volume into a single bounded oscillator. Unlike OBV or the A/D Line, MFI oscillates on a fixed scale, making overbought and oversold readings easy to identify. However, the bounded nature means MFI can sometimes signal overbought conditions during powerful trend moves where the trend still has room to run. Combining MFI with a trend indicator like ADX helps identify whether overbought readings represent exhaustion or simply strong momentum.