1. Cause, not result: where this rule fits in discourse
Because of and due to introduce the CAUSE of an event, as do the conjunctions because, since, and as. The difference is purely structural: because/since/as connect a complete subordinate clause (subject + verb), whereas because of and due to are prepositional phrases followed by a noun, noun phrase, or -ing form.
This rule is not about results: therefore, as a result, and consequently (a neighboring rule in this topic) introduce a RESULT in a separate sentence after the cause has already been stated. Because of / due to, by contrast, stand next to the cause within the same sentence as the main event.
Because of / Due to + [cause noun], main event
- noun —
- A word naming a person, thing or idea: student, book, happiness.
Because of a mix-up with the room booking, the interview was moved to Thursday.
Because of the confusion over the room booking, the interview was moved to Thursday.
The noun phrase a mix-up with the room booking is the cause, not the result; the result (the move) is in the main part of the same sentence.
The museum stayed open later due to unusually high visitor numbers.
The museum stayed open later due to an unusually high number of visitors.
Due to appears in the middle of the sentence, directly before the noun phrase—the cause—not in a separate result sentence.
2. A noun phrase or -ing construction instead of an ordinary sentence
After because of / due to, you can use a noun phrase or an -ing construction: heavy traffic, a two-hour delay, the printer breaking down. The last one has an explicit subject, the printer, but no finite verb such as broke. The ordinary form because of the printer broke down is not a correct pattern.
This is the most common B1 mistake: a learner remembers because of / due to as a synonym for because and simply adds a clause without making any changes. But the preposition requires a noun element—just as after school (a noun) differs from after I finished school (a clause introduced by the different conjunction after).
Because of / Due to + [noun / noun phrase / -ing form], NOT [subject + verb]
- subject / S —
- The grammatical subject: who or what the clause is about; the verb agrees with it. In The book was written, the book is the subject, although someone else does the action.
- verb / V —
- A word for an action or state, such as work or be. The pattern determines its form.
- V-ing / -ing —
- The verb form ending in -ing: working, going. Its role depends on the construction.
- NP / noun phrase —
- A noun phrase: a noun with its dependent words, such as the new student; the pattern treats it as one group of words.
- noun —
- A word naming a person, thing or idea: student, book, happiness.
Due to a shortage of parking spaces, the office asked staff to use public transport.
Because of a shortage of parking spaces, the office asked staff to use public transport.
A shortage of parking spaces is a noun phrase, not the clause there weren't enough spaces.
Because of the noise from the construction site, the class moved to a quieter room.
Because of the noise from the construction site, the class moved to a quieter room.
The noise from the construction site is a noun phrase with additional information; the clause it was noisy would not fit here without changing the form.
Due to heavy rain overnight, the outdoor concert was moved indoors.
Due to heavy rain overnight, the outdoor concert was moved indoors.
Heavy rain overnight is a noun phrase with a time adverb, still without its own verb.
3. Nominalization: how to condense a cause sentence into a noun phrase
A cause often first exists as a sentence: “Someone was late,” “The system failed.” To use because of / due to, turn the action into a noun from the same word family: be late → lateness/delay, fail → a failure, break down → a breakdown, cancel → a cancellation.
Sometimes there is no convenient one-word noun, and it is more natural to add an adjective to an existing noun: it rained heavily → the heavy rain; the meeting was long → the length of the meeting. The key is to preserve the fact, not just the word: heavy rain and a downpour can describe the same event, while delay and postponement are different (the first means lateness, the second means moving something to another time).
Because of a sudden drop in temperature, the pipes froze overnight.
Because of a sudden drop in temperature, the pipes froze overnight.
A sudden drop in temperature is a nominalization of the sentence “the temperature suddenly dropped.”
The flight was rerouted due to a technical problem with the aircraft.
The flight was rerouted due to a technical problem with the aircraft.
A technical problem is a nominalization of “something was technically wrong”; use problem, not failure, because the situation is described generally, not as a complete breakdown.
Because of the popularity of the new menu, the restaurant extended its opening hours.
Because of the popularity of the new menu, the restaurant extended its opening hours.
The popularity is a nominalization of “the menu became popular”; this is an example of a positive cause, not only a problem.
4. When an -ing form is needed: a cause without a ready-made noun
If an action has no convenient noun (or if it is important to name the specific person who performed it), it is more natural to use an -ing form: because of the printer breaking down, due to him missing the deadline.
When the subject of the -ing form is a different person from the subject of the main clause, that subject must be named. In conversational style, an object pronoun or noun is natural (because of him being late, because of the manager forgetting); in more formal style, a possessive is used (because of his being late, because of the manager's forgetting). Both versions are grammatical; formal style more often chooses the possessive.
Because of the printer breaking down twice this week, we switched to a different one.
Because the printer broke down twice this week, we switched to a different one.
The printer breaking down is an -ing form because there is no short, ready-made noun for “broke down twice.”
Due to him forgetting the tickets, we had to go back home first.
Because he forgot the tickets, we had to go back home first.
Him forgetting uses an object pronoun before the -ing form; his forgetting would sound more formal, but both versions are correct.
Because of my sister constantly checking her phone, we missed the beginning of the film.
Because my sister was constantly checking her phone, we missed the beginning of the film.
My sister is the stated subject of the -ing form checking because it is not the same subject as we in the main clause.
5. Due to versus because of: register, not meaning
Because of and due to mean the same thing and take the same form. The difference is register: due to (as well as owing to) is more typical of formal writing, announcements, and news; because of works in both conversation and writing.
Historically, some style guides required due to to appear only after the verb be (the delay was due to bad weather), as an adjective phrase rather than as a preposition at the beginning of a sentence. Today, due to at the beginning of a sentence (Due to bad weather, the match was postponed) is so widespread and accepted that it is considered standard; we do not mark this position as an error.
Everyone agreed the hold-up was due to a last-minute change in the schedule.
Everyone agreed the hold-up was due to a last-minute change in the schedule.
Due to appears here after was—the position that style guides once required.
Due to a last-minute change in the schedule, the delay affected several trains.
Due to a last-minute change in the schedule, the delay affected several trains.
The same due to at the beginning of a sentence is a modern standard, not an error.
6. Position and comma
The because of / due to phrase can come at the beginning of a sentence (in which case it is followed by a comma separating it from the main clause) or in the middle or at the end (in which case a comma is generally not needed).
Its position does not change the form of its complement: a noun or -ing form is needed in both cases. The choice of position depends on what you want to emphasize first: the cause or the event.
At the beginning: Because of/Due to + X, main clause. In the middle/at the end: main clause + because of/due to + X (no comma).
- clause —
- A construction with a verb, often with its own subject: when I arrived. A non-finite clause may leave the subject unspoken: to get home.
Because of the strong winds, all ferry crossings were cancelled for the day.
Because of the strong winds, all ferry crossings were cancelled for the day.
A comma comes immediately after the phrase when it appears at the beginning of the sentence.
All ferry crossings were cancelled for the day because of the strong winds.
All ferry crossings were cancelled for the day because of the strong winds.
The same phrase appears at the end of the sentence, with no comma before because of.
7. Contrast with because / since / as + a clause
When the information has already been given as a complete sentence with a subject and verb (for example, in something another speaker has said), it is simplest to keep it as a clause with because, since, or as (see the neighboring rule about these conjunctions for details). Convert it to because of / due to when the cause has already been formulated as an event noun or when a shorter, more formal, or more written version is needed.
Both methods are grammatically correct for the same situation; the choice is stylistic, not about meaning. Therefore, in this rule we do not declare because + a clause to be wrong—we are simply practicing when a prepositional form is needed instead.
Because the ferry was delayed, we missed our connecting bus.
Because the ferry was delayed, we missed our connecting bus.
The clause the ferry was delayed belongs to the neighboring rule; here it is grammatically correct and appropriate.
Because of the ferry delay, we missed our connecting bus.
Because of the ferry delay, we missed our connecting bus.
The same meaning is nominalized in the ferry delay—the form practiced in this rule.
8. A common mistake and transfer to speaking
Do not leave an ordinary sentence immediately after due to or because of: Due to the shop was closed… You can name the cause with a noun (due to the shop’s closure), use an -ing form, or switch to because the shop was closed. Another correct, though longer, pattern is due to the fact that the shop was closed.
In real speech, this construction appears constantly in transport announcements, work emails, news reports, and even friendly explanations for being late. Being able to quickly turn a cause clause into a noun or -ing form is a practical skill, not just a grammar exercise.
The store closed early due to a staff meeting.
The store closed early due to a staff meeting.
A staff meeting is the corrected noun form instead of the incorrect clause staff had a meeting.
I'll be a few minutes late because of a delayed bus.
I'll be a few minutes late because of a delayed bus.
A delayed bus is a short, natural noun phrase that is convenient for a quick explanation in speech.
Common mistakes
Incorrect:Due to it was snowing heavily, the buses stopped running.
Correct:Due to the heavy snow, the buses stopped running.
Due to requires a noun phrase, not a clause with its own subject it and the verb was snowing.
Incorrect:Because of the printer broke down, we sent the file by email instead.
Correct:Because of the printer breaking down, we sent the file by email instead.
Because of requires a noun or -ing form; the complete clause the printer broke down does not fit here.
Incorrect:Due to she was feeling unwell, the meeting was postponed.
Correct:Due to her feeling unwell, the meeting was postponed.
The subject of the clause (she) becomes a possessive/object pronoun (her) before the -ing form rather than remaining the subject of a clause.
Incorrect:The trail was closed because of it rained heavily all week.
Correct:The trail was closed because of the heavy rain all week.
This pattern requires the noun phrase the heavy rain all week. Heavy conveys the intensity of the rain; do not replace it without a reason with constant, which would emphasize continuity.
Incorrect:Because of him missed the flight, we changed the whole plan.
Correct:Because of him missing the flight, we changed the whole plan.
After the stated subject (him), the verb takes the -ing form (missing), not the finite past-tense form (missed).