What it means
Technical analysis studies price and volume history to judge where a security may be heading. The MFI is sometimes called the volume-weighted version of the relative strength index.
Because it includes volume, it asks not just whether prices are rising but whether real money is behind the move. For each day, analysts first compute the typical price, the average of the high, low and closing prices.
Multiplying this by that day's volume gives the raw money flow. Days when the typical price rises count as positive flow, and days when it falls count as negative flow.
Over a set period, usually 14 days, the positive and negative flows are added up and compared as a ratio. That ratio is then converted into the 0 to 100 scale.
A high reading suggests heavy buying that may be stretched, while a low reading suggests heavy selling that may be exhausted. Traders also watch for divergence, which is when the price makes a new high but the MFI does not.
That mismatch can hint that the rally is losing support. It is a warning to look closer rather than a guaranteed signal.
The indicator has limits. In a strong trend it can stay above 80 or below 20 for a long time, so acting on the thresholds alone can mean selling too early.
It is best used with other evidence such as earnings news, trend lines and wider market conditions. Note also that MFI sometimes stands for microfinance institution, a lender serving low-income clients, which is a different concept.
In charts and trading platforms the abbreviation almost always means the Money Flow Index, so context settles the meaning quickly.
In practice
Real-world examples.
Example
A retail investor sees a stock rise for two weeks and checks the MFI, which reads 85. She interprets this as a sign of stretched buying and decides to wait for a pullback before adding to her position. A week later, the stock dips 6% and she buys at a lower price.
Example
A commodities trading desk analyst notices that a metal's price is making new highs while its MFI is falling. She reads this as weakening conviction behind the rally and tells her manager to tighten risk limits. The desk trims its position before prices reverse.
Example
A small business owner holds shares in a supplier and uses the MFI to time a sale. The indicator drops to 15 after a heavy sell-off, which suggests selling may be overdone. He holds on rather than selling at the lows, and the price recovers over the next month.
Formula
Calculation
Typical price = (High + Low + Close) / 3; Raw money flow = Typical price x Volume; Money flow ratio = Sum of positive money flow / Sum of negative money flow; MFI = 100 - (100 / (1 + Money flow ratio))
Suppose a day has a high of $52, a low of $48 and a close of $50, with 2,000,000 shares traded. The typical price is (52 + 48 + 50) / 3 = $50, so raw money flow is 50 x 2,000,000 = $100,000,000. Now suppose that across the last 14 days positive money flow totals $800,000,000 and negative money flow totals $200,000,000. The ratio is 800,000,000 / 200,000,000 = 4. The MFI is 100 - (100 / (1 + 4)) = 100 - 20 = 80, which is at the overbought threshold.Case study
Seen in the real world.
Lakeshore Capital Partners is an illustrative, fictional investment club with 25 members who meet monthly to review their portfolio. A newer member proposes using the Money Flow Index to decide when to buy and sell. The group agrees to test the idea on paper before using real money.
Over six months, the members record the reading for each holding at every monthly meeting and note what the price did over the following four weeks. They find that readings above 80 sometimes preceded falls but sometimes did not, particularly during strong earnings seasons. Readings below 20 gave mixed results as well, and the sample of only 25 holdings was too small to prove anything either way.
In this illustrative case, the club concludes that the indicator is helpful as one input but unreliable alone. They agree to check news and company results first, and use the MFI only to decide how quickly to act.
Watch out
Common mistakes.
- Selling automatically whenever the reading crosses 80, even though strong trends can keep it elevated for weeks.
- Ignoring volume data quality, which can be unreliable for some thinly traded securities.
- Confusing the Money Flow Index with the relative strength index, when the first includes volume and the second does not.
Questions
People also ask.
What period does the MFI normally use?
A 14-period setting is the common default, though traders adjust it to suit their time frame, using shorter periods for quicker signals and longer ones for steadier readings.
What is the difference between MFI and RSI?
The relative strength index uses price only, while the MFI weights each move by trading volume.
Does MFI predict the future?
No, it summarises past price and volume pressure, so it offers clues about momentum but no guarantees.
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