The French futur simple and the english will future both point to later events. But english uses will far more. French often avoids its own future tense, using the present tense instead. This happens when the future is already clear from context.

The main difference is this: French needs a future tense less often because time markers or logical links can do the work. English requires will in many places where French stays in the present.

French uses present instead of futur simple

French uses the present tense after quand (when), dès que (as soon as), pendant que (while), aussitôt que (as soon as), tant que (as long as), and si (if) when the main clause is future.

Quand tu arriveras, je serai parti – “When you arrive, I will have left” (French uses future in main clause, present in subordinate clause)
Dès qu’il pleut, on reste à la maison – “As soon as it rains, we stay home” (habitual)
Si tu viens, je serai content – “If you come, I will be happy”

English uses will in the main clause but present tense in the when or if clause. French keeps the present in both if the meaning is clear.

French also uses the present for planned future actions near in time, especially with a time word.

Je pars demain – “I am leaving tomorrow”
On se voit lundi – “We will see each other on monday”
Le train arrive dans cinq minutes – “The train will arrive in five minutes”

English could use will here but often prefers present continuous (is arriving) or simple present for schedules. French has no present continuous for future, so the simple present does the job.

French uses futur simple but english uses present

This is rare. But after pendant que (while), French uses future if the main clause is future. English uses present.

Pendant que tu dormiras, je travaillerai – “While you sleep, I will work”

When english uses will but French uses futur simple similarly

Both use the future tense for predictions without a time word.

Il fera beau demain – “The weather will be nice tomorrow”
Tu verras, elle réussira – “You will see, she will succeed”

Both use the future for promises or offers.

Je t’aiderai – “I will help you”
On paiera plus tard – “We will pay later”

Both use the future for polite requests or uncertainty.

Tu viendras nous voir, j’espère – “You will come see us, I hope”
Ce sera peut-être trop tard – “That will perhaps be too late”

English uses will but French uses aller + infinitive

The near future (futur proche) with aller (to go) often replaces futur simple in spoken french. English can use going to or will.

Je vais le faire – “I will do it” or “I am going to do it”
On va manger – “We will eat” or “We are going to eat”

For very near future with a time word, french prefers aller over futur simple.

Je vais appeler tout de suite – “I will call right now”

English uses present but french uses futur simple

English can use present tense after when, as soon as, after, before, until in future meaning. French must use futur simple in the same clauses.

I will call you when I arrive – Je t’appellerai quand j’arriverai
We will eat after you finish – Nous mangerons après que tu auras fini (note: après que requires futur antérieur or futur simple in careful French)

Before he comes, we will clean – Avant qu’il vienne, nous nettoierons (here vienne is present subjunctive, not future; French avoids future after avant que)

Summary

English uses will in most future contexts. French avoids futur simple in four main ways:

• Present tense after time words like quand, dès que, pendant que, and si when the main clause is future.
• Present tense for planned future actions with a time marker.
• Aller + infinitive for near future, especially in speech.
• Present tense in many cases where english uses will but the future is already clear.