When you want to talk about the future in English, one question helps you choose between be going to and will:
Was the decision made before this moment, or at this moment?
If the decision, plan, or intention existed before you opened your mouth — you already had it in your mind — use be going to. If the decision happens at the moment of speaking — you are reacting to something, making an offer, or choosing right now — use will.
| Situation | Form | Example |
|---|---|---|
| Pre-decided plan or intention | be going to | I am going to visit my parents this weekend. (decided earlier) |
| Evidence-based prediction (you can see/hear/feel it) | be going to | Look — it is going to rain. (dark clouds visible) |
| Spontaneous decision at the moment of speaking | will | "The phone is ringing." — "I will answer it." (decided right now) |
| Spontaneous offer or promise | will | "You look tired." — "I will make you a coffee." (decided right now) |
| General opinion or prediction (no visible evidence) | will | I think electric cars will replace petrol cars. (general belief) |
The decision is already made. You are not choosing at this moment — you are reporting a plan, intention, or arrangement that already exists. There is often supporting evidence: a booking, a conversation that already happened, something that has already been set in motion.
You can see, hear, or feel something right now that tells you a future event is imminent. This is not an opinion — it is a conclusion drawn from present evidence.
Something happens or is said, and you decide what to do right now, in response. The decision did not exist before this moment — it is created by the situation you are in right now.
You hear something — a need, a problem, a worry — and you immediately respond with an offer or a promise. The offer is created at this moment, not planned in advance.
When you share a belief or prediction about the future based on general knowledge, reasoning, or opinion — with no specific visible evidence right now — you use will.
✗ "The phone is ringing." — "I am going to answer it."
✗ "You look cold." — "I am going to make you some tea."
✓ "The phone is ringing." — "I will answer it."
✓ "You look cold." — "I will make you some tea."
Be going to means the plan already existed. If you are reacting to something you just heard or just noticed — making a decision because of the current moment — that decision did not exist before. Use will. The test: could you have said this sentence five minutes ago? If no — use will.
✗ "She'll study medicine — she has already applied." (sounds like a prediction, not a plan)
✗ "We'll move next year." (sounds spontaneous — as if decided right now)
✓ "She is going to study medicine — she has already applied."
✓ "We are going to move next year." (plan already made)
When supporting information tells us the decision was made in advance — she has already applied, they signed the contract, he enrolled last week — the correct form is be going to. Using will in these contexts makes the plan sound like a new, spontaneous idea rather than a pre-existing intention.
✗ Watch out — it will fall! (the glass is on the edge right now)
✗ Look at those clouds — it will rain. (you can see the clouds)
✓ Watch out — it is going to fall!
✓ Look at those clouds — it is going to rain.
When you have present, visible evidence — something you can see, hear, or feel right now — the prediction is based on that evidence and the outcome is almost certain. This calls for be going to. Will is for predictions based on general belief or opinion, without current visible evidence. The key word is Look or Watch out — these almost always signal be going to.
✗ I think electric cars are going to replace petrol cars. (said as a general opinion, no current evidence visible)
✓ I think electric cars will replace petrol cars. (general opinion / prediction)
✓ Look at the sales figures — electric cars are going to replace petrol cars. (if you have evidence)
When a sentence begins with I think, I believe, I expect, probably, maybe — these signal that the speaker is sharing a general opinion about the future. This is the territory of will. Be going to is possible here too, but will is the more natural and common choice for general predictions and opinions without specific present evidence.