Every time you use will for an intention, the key is that the decision, offer, or promise is being made at the exact moment of speaking. There is no prior plan. There is no advance arrangement. You are responding to what is happening right now — a need, a request, a moment — and deciding in real time.
This is what separates will from going to. Going to describes intentions and plans that were decided before the current conversation. Will describes decisions that are born during the conversation — in the moment, on the spot.
An offer is a response to a need you observe in the moment. You see someone struggling, tired, cold, or in difficulty — and you volunteer to help right then.
A promise is a commitment made in response to a request, a fear, or a concern expressed by someone else. The promise is formed at the moment of hearing the concern.
A spontaneous decision is made when you encounter a situation — often a problem or a choice — and decide what to do right at that moment, not before.
| WILL — spontaneous | GOING TO — pre-planned |
|---|---|
| Decided now, while speaking | Decided before the conversation |
| Response to what you observe or hear right now | A plan or intention already in place |
| "The door's open — I'll close it." | "I'm going to paint the door this weekend." (planned) |
| "I'll call you." (offer / promise in this moment) | "I'm going to call my mum later." (scheduled plan) |
| "Shall I help?" "Yes — I'll help." | "I've arranged to help them move house." |
✗ "The phone is ringing — I'm going to get it." · "You look tired — I'm going to make you tea." · "I'm going to have the soup." (deciding now)
✓ "The phone is ringing — I'll get it." · "You look tired — I'll make you tea." · "I'll have the soup."
When the decision is made at the moment of speaking — triggered by something you notice, hear, or are asked — use will. Going to implies the decision was made before this moment. A spontaneous offer or on-the-spot choice cannot be going to because you had not planned it in advance.
✗ "I will visit my parents next weekend — we booked the train months ago." · "I will move to a new apartment — I signed the contract last week."
✓ "I'm going to visit my parents next weekend — we booked the train months ago." · "I'm going to move to a new apartment — I signed the contract."
When there is evidence of prior planning — a booking, an agreement, a signed contract, an existing arrangement — use going to. The use of will for pre-planned intentions sounds odd to a native speaker and is one of the most commonly tested distinctions at B1–B2 level.
✗ "I promise I'm going to call you every day." · "I'm going to always be there for you." · "It's going to be fine — I'm going to fix everything."
✓ "I promise I'll call you every day." · "I'll always be there for you." · "It'll be fine — I'll fix everything."
Promises are commitments made at the moment of speaking, in response to a worry, request, or situation. Because they are made now — not in advance — they use will. A promise with going to sounds like a plan, not a commitment. The word promise itself signals that will is required.
✗ "I carry that for you." · "I make you a cup of tea." · "I get the phone."
✓ "I'll carry that for you." · "I'll make you a cup of tea." · "I'll get the phone."
In English, you cannot use the Present Simple to express a spontaneous offer or future decision. The Present Simple describes habitual actions or permanent facts, not future intentions. Spontaneous offers and decisions always require will + base verb. This error is very common among speakers of Romance languages, where the present tense is often used for offers.