Glossary term
Money Flow Index (MFI)
The Money Flow Index is a volume-weighted momentum oscillator that compares positive and negative money flow over a chosen period.
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What Is the Money Flow Index (MFI)?
The Money Flow Index, or MFI, is a volume-weighted momentum oscillator used in technical analysis. It compares positive and negative money flow over a chosen lookback period to estimate whether buying or selling pressure is strengthening.
MFI is sometimes described as a volume-weighted cousin of the relative strength index. RSI uses price changes. MFI uses both price and volume, which makes it useful when traders want to know whether price movement is supported by participation.
Key Takeaways
- MFI is a technical oscillator that ranges from 0 to 100.
- It uses typical price and volume to estimate positive and negative money flow.
- Readings above 80 are often treated as overbought and readings below 20 as oversold, though context matters.
- Divergences between MFI and price can warn that a trend is losing participation.
- MFI is a signal tool, not a complete trading system.
MFI Formula
The calculation starts with typical price:
Raw money flow is typical price multiplied by volume. Positive money flow comes from periods where typical price rises from the prior period; negative money flow comes from periods where typical price falls.
The money flow ratio is positive money flow divided by negative money flow over the lookback period. A common setting is 14 periods, but traders may adjust the lookback based on time frame and instrument.
How Traders Read It
An MFI reading near the high end of the range can indicate strong buying pressure, but it can also signal that a security is stretched. A reading near the low end can indicate strong selling pressure or a potentially washed-out condition. The same number can mean different things in a strong trend versus a choppy market.
Divergence is often more useful than the raw level. If price makes a new high while MFI fails to confirm, participation may be weakening. If price makes a new low while MFI holds up or rises, selling pressure may be fading. These signals still need price confirmation.
Practical Chart Use
MFI behavior | Possible interpretation |
|---|---|
Price up, MFI up | Advance may be supported by volume. |
Price up, MFI down | Potential bearish divergence. |
Price down, MFI down | Decline may be supported by selling pressure. |
Price down, MFI up | Potential bullish divergence. |
Signal Quality
MFI can stay overbought during a powerful advance and oversold during a persistent decline. Treating 80 or 20 as automatic trade triggers can lead to premature entries. The indicator works best with support and resistance, trend structure, volume context, and risk controls.
Volume quality also matters. Thinly traded securities, one-off block trades, index rebalances, or event-driven spikes can distort the indicator. The MFI line is evidence about participation, not proof that price must reverse.
Time frame matters as much as the threshold. A 14-day MFI on a daily chart may help a swing trader, while an intraday chart may be more vulnerable to opening volume, closing auctions, and news bursts. A longer lookback smooths noise but reacts later. A shorter lookback reacts faster but throws more false signals. The useful test is whether the indicator improves decisions after transaction costs and stop placement, not whether it marks every local high or low in hindsight.
Confirmation is especially important around earnings, macro releases, and sector-wide moves. In those settings, volume may reflect event positioning rather than a durable shift in supply and demand. Many traders wait for price to break a level, reclaim a moving average, or fail at resistance before treating an MFI divergence as actionable.
The Bottom Line
The Money Flow Index measures volume-weighted buying and selling pressure on a 0-to-100 scale. It can help confirm trends or spot divergences, but it should be read with price action, liquidity, trend context, and a clear risk plan.