Vocabulary size at each IELTS band

As part of BRAVE validation, we studied how measured vocabulary size correlates with IELTS scores. We had 2,004 respondents who reported their recent IELTS scores. Here are some preliminary results.

Data insights

As one progresses in English, it takes about 1,500 words to gain each additional IELTS band, at least up to the C1 level (IELTS 4.0–7.0).

It gets much harder at C1 and higher. To gain an IELTS band by going from mid-C1 (IELTS 7.5, 8,400 words) to C2 (IELTS 8.5, 13,100 words), one needs to learn 4,700 new words — 3 times more than for the bands before.

Who the respondents are

CEFR level	N	Median age	Age 10–90% range	Top 10 countries
B1	28	20	14–27	Kazakhstan 39%, Vietnam 14%, Uzbekistan 11%, Russia 7%, Kyrgyzstan 7%, United States 4%, Germany 4%, Canada 4%, The Netherlands 4%, Malaysia 4%
B2	536	22	17–31	Kazakhstan 37%, Russia 5%, United States 5%, Uzbekistan 5%, Vietnam 4%, Germany 4%, United Kingdom 4%, The Netherlands 2%, Italy 2%, Ukraine 2%
C1	1,258	24	18–33	Kazakhstan 20%, Germany 8%, United States 5%, The Netherlands 5%, Vietnam 5%, United Kingdom 5%, Uzbekistan 4%, Russia 4%, Italy 3%, France 2%
C2	182	26	20–34	Germany 10%, United Kingdom 7%, Canada 6%, Kazakhstan 6%, United States 6%, France 4%, Australia 4%, Hong Kong 3%, Switzerland 3%, Russia 3%

Notes

• The data were collected between November 2025 and August 2026.
• Data were cleaned to remove sessions with low response quality: more than 1 fake item checked, more than 3 multiple-choice follow-up questions answered incorrectly, response time too fast (<40 s) or too slow (>300 s). Only the first attempt per user was retained.
• IELTS scores are self-reported. CEFR levels were assigned based on the official IELTS-to-CEFR conversion guide.
• BRAVE measures receptive vocabulary — words we understand but do not necessarily use ourselves.
• Results are in word families, so related forms such as limit, limitation, and limitless are counted together.