Vocabulary Size for Fluency Calculator

Vocabulary size by CEFR level and text coverage

Work on vocabulary size by people like Paul Nation, plus the Cambridge English Profile and Lextale, gives us a rough map of active vocabulary at each CEFR level. A1 sits around ~500 words, A2 near ~1.000, and B1 climbs to 2.000–3.000. From there it's B2 at 4.000–5.000, C1 at 8.000–10.000, and C2 at 16.000+, with recognition vocabulary often pushing past 25.000+. There's a useful milestone hiding in the frequency data. The 2.000 most common word families already cover about 80% of an ordinary text; the top 5.000 take you to ~95%, and you'll want 8.000–9.000 to hit ~98%, which is roughly where you can start reading without a dictionary. So, example: if 95% coverage in English is your goal, you're looking at studying around 5.000 word families. That's a solid B2, and B2 happens to be what most companies ask for in international roles.

Applications

People use these numbers to set goals in spaced repetition systems like Anki SRS and RemNote, in gamified apps such as Duolingo and Memrise, and when planning frequency-based decks (say, the 5.000 most common words). On the business side, the usual target is B2 for working English, around ~4.000–5.000 words, and C1 once you need an executive or academic register. It also helps you weigh extensive reading, which builds broad recognition, against intensive drilling that pushes words into active output.

FAQ

What is the difference between active and passive vocabulary? Active is what you can actually produce when you speak or write. Passive, or recognition, is what you understand while reading or listening. The passive set usually runs 2–3× bigger than the active one.

What is a "word family"? It's a base word together with its inflections and the derivatives that grow out of it. So nation, national, nationalize, nationality all count as a single family.

How many words per day for fluency? Learning 10–20 new words a day with spaced repetition will usually get you to B2 in 12–18 months. Showing up every day matters more than cramming a lot at once.

Does Duolingo teach enough vocabulary? Finish the full tree and you're at roughly ~3.000–4.000 words. That covers B1 but falls short of B2, so you'll need reading and listening to fill the gap.