What is Momentum? Definition, Formula, and Example
Momentum is the rate of acceleration of a security's price, measuring how quickly price is changing over a defined lookback period rather than the direction of the change alone.
What is Momentum?
Momentum is the speed of price change. In physics terms, if price is position, momentum is velocity. A stock that rose from 100 to 110 over ten days has positive momentum; if it then rises from 110 to 113 over the next ten days, price is still rising but momentum is decelerating. That distinction is the entire value of the concept: momentum often turns before price does, which is why momentum indicators are used to anticipate exhaustion in trends and to confirm the strength of new ones. Momentum is also an academic factor: the cross-sectional momentum effect, where recent winners keep winning for 3 to 12 months, is one of the most documented anomalies in finance.
How Momentum is Calculated
The simplest momentum indicator is a raw difference:
Momentum = Close_today - Close_n periods ago
A normalized version is rate of change: ROC = ((Close_today / Close_n periods ago) - 1) x 100. A 14-period lookback is a common default. Most popular oscillators are refinements of this idea. RSI normalizes momentum into a 0-100 band by comparing average gains to average losses. MACD measures momentum as the spread between two exponential moving averages. Stochastic locates the close within the recent high-low range. All answer the same question: is price change accelerating or decelerating?
Worked Example
Suppose NVDA closes at 800 today and closed at 740 fourteen sessions ago. Raw momentum is +60 points, and ROC is (800/740 - 1) x 100 = 8.1%. Two weeks later the stock closes at 830, but the 14-day-ago close is now 810. Price made a new high, but momentum fell to +20 points and ROC dropped to 2.5%. That is bearish divergence: price rising on fading momentum, a classic warning that the trend is losing fuel. The reverse setup is equally useful: if AMD grinds sideways while its 14-day momentum climbs from -5 to +12, sellers are losing control and a breakout becomes more probable.
When Traders Use It
Momentum serves three jobs. First, trend confirmation: a breakout from consolidation with momentum at multi-week highs is far more reliable than one with flat momentum. Second, exhaustion signals: divergence between price and momentum flags potential reversals before they appear on the price chart. Third, systematic ranking: momentum traders screen the entire market by 3, 6, or 12-month ROC and concentrate capital in the top decile, rebalancing monthly. Short-term traders use intraday momentum, measured by ROC on 5-minute bars or by relative volume, to find names with genuine institutional participation rather than thin drift. You can rank the whole market by momentum characteristics on the live scanner.
Limitations and Common Misconceptions
Momentum is a coincident indicator dressed as a leading one. Divergences can persist for weeks while price keeps making new highs, so divergence alone is a warning, not a sell signal. Momentum crashes are real: the factor suffers violent drawdowns at market turning points, because recent winners are the most crowded shorts' targets and the most exposed longs. The lookback period dominates results: a 14-day and a 200-day momentum read on the same stock routinely contradict each other, and neither is "wrong." Finally, momentum says nothing about value; a stock can have superb momentum and be wildly overpriced, which is exactly the condition that produces blow-off tops.