ppm和ppt定義為：
1ppm = 1/10 6 = 10 -6
1ppt = 1/10 12 = 10 -12
所以
1ppm = 10 6個百分點
每兆萬分率x ppt的數量等於百萬分之一x ppm的數量乘以10 6：
X的ppt = X ppm的⋅10 6
示例：7ppm等於7000ppb：
x ppt = 7ppm⋅10 6 = 7000000ppt
| ppm | ppt |
|---|---|
| 0.000001 | 1 |
| 0.00001 | 10 |
| 0.0001 | 100 |
| 0.001 | 1000 |
| 0.01 | 10000 |
| 0.1 | 100000 |
| 1 | 10 6 |
| 10 | 10 7 |
| 100 | 10 8 |
| 1000 | 10 9 |
| 10000 | 10 10 |