"Due to" modifies a NOUN (acts as an adjective); "because of" modifies a VERB or the whole sentence (acts as an adverb). In modern informal English many use them interchangeably, but formal English distinguishes them.
DUE TO: prepositional phrase functioning as an ADJECTIVE — it modifies a noun. The classic test: if you can replace it with "caused by" and it makes logical sense, use DUE TO. "The delay was due to traffic" = the delay was caused by traffic. "Due to" modifies the noun "delay." DUE TO always follows a copular verb (be, seem, appear) or a noun. "The cancellation, due to heavy rain, was announced yesterday" = the cancellation (noun) attributed to (due to modifies "cancellation"). In formal English (documents, official letters, press releases), DUE TO is preferred when the subject of the sentence is the effect: "The flight delay was due to fog."
The product launch delay was entirely due to supply chain disruptions that affected three of the company's primary component manufacturers.
The high employee retention rate at the firm is largely due to a combination of competitive compensation, flexible working arrangements, and strong team culture.
The variance in the quarterly results was due to an accounting adjustment that was identified during the external audit and required retroactive correction.
BECAUSE OF: prepositional phrase functioning as an ADVERB — it modifies a verb or the whole sentence. "She left early because of the traffic" = she left early (verb: left) because of (because of modifies the act of leaving). BECAUSE OF can go at the BEGINNING of a sentence: "Because of the traffic, she left early." DUE TO at the beginning of a sentence is more disputed in formal English (though very common). Functional difference: "The meeting was cancelled DUE TO rain" = noun (the meeting) + was + due to (adjective). "They cancelled the meeting BECAUSE OF rain" = verb (cancelled) + because of (adverb). In COLLOQUIAL English, DUE TO and BECAUSE OF are used interchangeably — the distinction is mainly FORMAL and ACADEMIC.
The project team had to restructure their entire timeline because of unforeseen technical dependencies that were not identified during the initial scoping phase.
Because of the significant shift in consumer preferences toward sustainable products, the company has committed to redesigning its entire packaging strategy.
Several key hires were delayed because of a competitive talent market that made it challenging to attract candidates with the required technical expertise.
Common mistake
Classic errors: (1) "Because of the rain, the cancellation was expected" = grammatically questionable in formal English. If the subject is the EFFECT (the cancellation), DUE TO is correct: "Due to the rain, the cancellation was expected" or "The cancellation was expected due to the rain." (2) "The success of the project is because of good planning" = INCORRECT. After "is" (copular verb), the causal prepositional phrase should be DUE TO (adjectival): "The success is DUE TO good planning." BECAUSE OF goes with action verbs, not copular verbs linking a noun to its cause. (3) "Due to she left early" = INCORRECT. Both DUE TO and BECAUSE OF take NOUNS/GERUNDS, not subject+verb clauses: "due to her leaving early" (correct) or "because she left early" (correct with conjunction BECAUSE, not BECAUSE OF).
Trick to remember it
The NOUN TEST: find what the causal phrase modifies. If it modifies a NOUN (noun + was/is/were + cause) = DUE TO. If it modifies a VERB or the predicate of the sentence (subject + action verb + cause) = BECAUSE OF. "The failure WAS due to poor planning" = the failure (noun) + was (copula) + DUE TO. "They FAILED because of poor planning" = they failed (action verb) + BECAUSE OF. Second test: substitute with "caused by." If the logical support holds = DUE TO: "The failure was caused by poor planning." If you cannot substitute directly (because it modifies a verb) = BECAUSE OF.
Quick rule
Due to = modifies a NOUN (the result was due to the cause). Because of = modifies a VERB (the team acted because of the cause). Quick test: "caused by" -> if it fits = due to. Action verb as the core -> because of. In colloquial English, many natives use them interchangeably.
Did you know?
The grammatical distinction between DUE TO and BECAUSE OF is one of the longest-running disputes in prescriptive English. 20th-century purists insisted that DUE TO could only function as an adjective (modifying nouns), and that "due to the rain, she left" (modifying a verb) was incorrect. However, this "adverbial" use of DUE TO has existed in English since the 15th century and appears in canonical writers like Chaucer and Shakespeare. The prescriptive vs descriptive battle around DUE TO is a perfect example of how grammatical rules taught in schools sometimes contradict the actual historical use of the language. Today, most modern English usage manuals accept both uses, noting that the adjectival use is more formal and the adverbial use is colloquial.
Exercise 1 · Pick the right one
The underperformance of the southern region in Q3 was primarily _____ a combination of adverse weather conditions and an aggressive promotional campaign by the main competitor.
Exercise 2 · Pick the right one
The marketing team had to pivot their entire content strategy _____ a sudden and unexpected shift in the platform's algorithm that dramatically reduced organic reach.
Exercise 3 · Form the word
Due to = modifies a NOUN (the result was due to the cause). Because of = modifies a VERB (the team acted because of the cause). Quick test: "caused by" -> if it fits = due to. Action verb as the core -> because of. In colloquial English, many natives use them interchangeably.
Classic errors: (1) "Because of the rain, the cancellation was expected" = grammatically questionable in formal English. If the subject is the EFFECT (the cancellation), DUE TO is correct: "Due to the rain, the cancellation was expected" or "The cancellation was expected due to the rain." (2) "The success of the project is because of good planning" = INCORRECT. After "is" (copular verb), the causal prepositional phrase should be DUE TO (adjectival): "The success is DUE TO good planning." BECAUSE OF goes with action verbs, not copular verbs linking a noun to its cause. (3) "Due to she left early" = INCORRECT. Both DUE TO and BECAUSE OF take NOUNS/GERUNDS, not subject+verb clauses: "due to her leaving early" (correct) or "because she left early" (correct with conjunction BECAUSE, not BECAUSE OF).
The NOUN TEST: find what the causal phrase modifies. If it modifies a NOUN (noun + was/is/were + cause) = DUE TO. If it modifies a VERB or the predicate of the sentence (subject + action verb + cause) = BECAUSE OF. "The failure WAS due to poor planning" = the failure (noun) + was (copula) + DUE TO. "They FAILED because of poor planning" = they failed (action verb) + BECAUSE OF. Second test: substitute with "caused by." If the logical support holds = DUE TO: "The failure was caused by poor planning." If you cannot substitute directly (because it modifies a verb) = BECAUSE OF.
Bryan López
Founder of SpeakUP Academy