Money flow index
A volume-weighted version of RSI, combining price and volume into a 0–100 reading of buying/selling pressure — often called the “volume RSI.”
What the numbers mean
The lookback is the number of bars over which money flow — typical price times volume — is split into positive and negative and expressed on a 0–100 scale. It is RSI's calculation with volume weighting added, and 14 is the default for the same historical reason.
- 14 — the lookback, carried from RSI convention
- 80 / 20 — the usual extremes, set wider than RSI's because volume weighting makes it swing harder
- 90 / 10 — used for genuinely extreme readings
- 50 — the midline, read as with RSI
How it is used
Read like RSI, but with the extremes usually set wider at 80 and 20 because the volume weighting makes it swing harder. Divergence is the most-watched signal, since it means price and the money behind it are disagreeing.
- Above 80 → overbought with volume behind the move
- Below 20 → oversold
- Divergence against price → price and the money behind it disagreeing
- MFI overbought while RSI is not → the rally is heavily volume-driven
How it relates to everything else
MFI is RSI with volume weighting, which makes the pair unusually informative when read together: when they agree, price and participation are telling the same story; when they diverge, one of the two is doing the work. MFI swings harder, so its extremes come sooner and need wider thresholds.
- MFI = RSI + volume; comparing the two is the whole point
- MFI divergence + price at resistance → a common topping combination
- Jumpy around earnings and other heavy-volume sessions
What to watch for
The same trap as RSI: in a strong trend it can sit above 80 for a long time. Volume weighting also makes it jumpy around earnings and other unusually heavy sessions.