The 'simple' future (le futur or le futur simple) is a one-word tense. So it’s simple!
Use it to indicate an action that will be done in the future.
The endings for the simple future are: -ai , -as, -a, -ons, -ez, -ont.
For regular -er and -ir verbs:
Keep the infinitive (manger, finir) and add the future endings.
For regular -re verbs:
The stem is the infinitive (rendre, attendre), minus the final -e.
For -er verbs with spelling or accent changes:
Verbs like préférer (je préférerai), manger (je mangerai) and commencer (je commencerai) change spelling or accents in the future.
-er verbs with spelling changes in the present (appeler, employer, acheter) have irregular future stems.
**You will need to memorize these.
Use the futur simple…
1) To talk about the future. It is more formal than the futur proche, although you can use either in most contexts.
2) In sentences with quand and lorsque (when) or dès que (as soon as) if the action is the future. (Notice that this is different from English).
3) In if..then sentences when the si (if) is followed by a present-tense verb.
Irregular future stems
Some irregular verbs also have irregular future stems, but the future endings are the same for all verbs:
-ai , -as, -a, -ons, -ez, -ont.
The future stem for the verb être is ser- and the future stem for the verb avoir is aur-.
Here are the most common verbs that have irregular future stems: