| singular | plural |
| Infinitive | | |
| ascertain | |
| present simple | | |
| 1 | I ascertain | we ascertain |
| 2 | you ascertain | you ascertain |
| 3 | he/she/it ascertains | they ascertain |
| past simple | | |
| 1 | I ascertained | we ascertained |
| 2 | you ascertained | you ascertained |
| 3 | he/she/it ascertained | they ascertained |
| future simple | | |
| 1 | I will/shall ascertain | we will/shall ascertain |
| 2 | you will/shall ascertain | you will/shall ascertain |
| 3 | he/she/it will/shall ascertain | they will/shall ascertain |
| conditional simple | | |
| 1 | I would ascertain | we would ascertain |
| 2 | you would ascertain | you would ascertain |
| 3 | he/she/it would ascertain | they would ascertain |
| present continuous | | |
| 1 | I am ascertaining | we are ascertaining |
| 2 | you are ascertaining | you are ascertaining |
| 3 | he/she/it is ascertaining | they are ascertaining |
| past continuous | | |
| 1 | I was ascertaining | we were ascertaining |
| 2 | you were ascertaining | you were ascertaining |
| 3 | he/she/it was ascertaining | they were ascertaining |
| future continuous | | |
| 1 | I will be ascertaining | we will be ascertaining |
| 2 | you will be ascertaining | you will be ascertaining |
| 3 | he/she/it will be ascertaining | they will be ascertaining |
| conditional continuous | | |
| 1 | I would be ascertaining | we would be ascertaining |
| 2 | you would be ascertaining | you would be ascertaining |
| 3 | he/she/it would be ascertaining | they would be ascertaining |
| present perfect | | |
| 1 | I have ascertained | we have ascertained |
| 2 | you have ascertained | you have ascertained |
| 3 | he/she/it has ascertained | they have ascertained |
| past perfect | | |
| 1 | I had ascertained | we had ascertained |
| 2 | you had ascertained | you had ascertained |
| 3 | he/she/it had ascertained | they had ascertained |
| future perfect | | |
| 1 | I will have ascertained | we will have ascertained |
| 2 | you will have ascertained | you will have ascertained |
| 3 | he/she/it will have ascertained | they will have ascertained |
| conditional perfect | | |
| 1 | I would have ascertained | we would have ascertained |
| 2 | you would have ascertained | you would have ascertained |
| 3 | he/she/it would have ascertained | they would have ascertained |
