ppm和ppb定義為：
1ppm = 1/10 6 = 10 -6
1ppb = 1/10 9 = 10 -9
所以
1ppm = 1000ppb
每十億分之一的數量x ppb等於每百萬分之一的數量x ppm乘以1000：
X PPB = X ppm的⋅1000
示例：7ppm等於7000ppb：
x ppb = 7ppm⋅1000 = 7000ppb
| ppm | ppb |
|---|---|
| 0.001 | 1 |
| 0.01 | 10 |
| 0.1 | 100 |
| 1 | 1000 |
| 10 | 10000 |
| 100 | 100000 |
| 1000 | 1000000 |
| 10000 | 10000000 |