Learn the stock market › Volume and volatility › Lesson 2 of 5
How much does a stock move in a day?
Each company has its own normal day
Take the last 250 trading days, ignore whether the price went up or down, and take the middle of the moves. On half the days the stock moved less than that and on half more. That is the company's normal day. The middle isn't pulled by a few big days, which the standard deviation is.
| Company | Normal day | Swing per year |
|---|---|---|
| Berkshire Hathaway | 0.55% | 15.1% |
| Costco | 0.76% | 20.3% |
| Visa | 0.78% | 22.9% |
| JPMorgan Chase | 0.86% | 22.9% |
| Apple | 0.86% | 24.8% |
| Mastercard | 0.90% | 23.5% |
| Walmart | 0.90% | 26.9% |
| Exxon Mobil | 1.03% | 27.1% |
| Alphabet | 1.08% | 33.8% |
| Microsoft | 1.12% | 33.8% |
| Netflix | 1.17% | 36.3% |
| Eli Lilly | 1.26% | 35.4% |
| Amazon | 1.29% | 33.9% |
| Meta | 1.29% | 41.3% |
| Nvidia | 1.54% | 38.3% |
| Broadcom | 1.61% | 47.2% |
| Tesla | 1.75% | 45.6% |
| Palantir | 1.84% | 60.8% |
| Oracle | 2.45% | 59.3% |
| AMD | 2.48% | 72.0% |
The middle of the companies is 1.14%. The swing per year is the volatility from the previous lesson, worked out on the same days. It runs from 15.1% for Berkshire Hathaway to 72.0% for AMD.
Big days come more often than you would think
If daily moves followed a bell curve, a normal distribution, a day of five times the normal would be very rare. Here is how often it happened, counted on 76,315 trading days, each compared with the company's normal day over the year before:
| Move | Share of days | On a bell curve |
|---|---|---|
| More than two normal days | 21.9% | 17.73% |
| More than three normal days | 9.7% | 4.30% |
| More than five normal days | 2.6% | 0.07% |
A move of more than five normal days came on 2.6% of the days, about once every 39 trading days. On a bell curve it would have been 0.07%, once every 1,342. Reality gave about 34 times as many. That is why a measure built on the bell curve understates how big a single day can get.
Compare with the stock's own normal day
A move says most when it is set against the stock's own normal days. 3% in a day is a lot for Berkshire Hathaway, but not unusual for AMD. The span between the day's high and low is a different measure, ATR, covered in What is ATR?.
Test yourself
Stock A moves 0.7% on a normal day and stock B 1.7%. Both rose 3.5% today. For which was it bigger?
More figures are on the page for AMD.