MFI is RSI with volume baked in. Up-bar money flow uses the bar's volume as the weight for positive readings; down-bar money flow uses volume for negative readings. The result is a 0-100 oscillator similar in shape to RSI but sensitive to volume.

Formula

typical    = (high + low + close) / 3
raw_flow   = typical * volume
pos_flow   = sum of raw_flow on up bars (period)
neg_flow   = sum of raw_flow on down bars (period)
ratio      = pos_flow / neg_flow
mfi        = 100 - 100 / (1 + ratio)

Params

period - window for the flow sums. Default 14.

Output

Single column named after your indicator (e.g. mfi).

Common thresholds

Range	Meaning
> 80	Overbought (stricter than RSI's 70)
< 20	Oversold (stricter than RSI's 30)

MFI uses tighter thresholds than RSI because volume weighting makes extremes rarer.

Usage

Mean reversion with volume confirmation: buy mfi < 20, fade mfi > 80.
Trend confirmation: like RSI, sustained readings above 50 support an uptrend.
Divergence: same pattern as RSI/MACD, not auto-detected.

Pitfalls

Same as OBV and other volume-aware indicators: depends on accurate volume data, and venues with weak or missing volume produce unreliable MFI.