What Is a Vocabulary Size Test?

A vocabulary size test estimates how many words you know. Since nobody can be tested on every word in a language, these tests take a sample of words from different frequency levels, check which ones you know, and scale the result up. A typical result looks like "about 7,000 word families," a measure of vocabulary breadth rather than depth.

How vocabulary size tests work

Most tests share three design steps:

1. A frequency list. Words are ranked by how common they are in a large corpus and grouped into bands of 1,000.
2. Sampling. A fixed number of words is drawn from each band.
3. Scaling. Your success rate in each band is multiplied up to that band's size, and the bands are summed.

The counting unit matters a great deal. Some tests count word families (decide, decision, decisive = one family), others count lemmas or individual word forms, and the same person can get very different numbers depending on the unit.

Major test types

The yes/no format is fast and can cover many words, but needs pseudowords (such as flanderate) to catch overclaiming. Multiple-choice tests allow lucky guesses, which inflate scores somewhat.

A worked example

What your score means

A size estimate is most useful compared with what you want to do:

• About 2,000–3,000 word families covers most everyday conversation.
• For comfortable, unassisted reading, research suggests about 98% lexical coverage (Hu & Nation, 2000), which for novels and newspapers means around 8,000–9,000 word families (Nation, 2006).
• Educated native speakers know many more: about 17,000 base words in Goulden, Nation and Read (1990), or roughly 42,000 lemmas in Brysbaert et al. (2016), depending on counting method.

See how many words you need to be fluent for more, and the CEFR entry for how size relates to levels.

How to use a vocabulary size test well

1. Take a test that reports results by frequency band, not just a single number.
2. Answer honestly; skip words you do not know rather than guessing wildly if the test allows it.
3. Find the first band where your score drops below about 85–90%; that is your learning frontier.
4. Focus study on words from that band, ideally met in reading.
5. Retest every few months to measure growth.

You can get a quick estimate with the vocabulary size estimator, and see how daily learning adds up with the vocabulary growth calculator.

Common misconceptions

• "The number is exact." It is an estimate with a margin of error, often several hundred words or more.
• "Knowing a word is yes or no." Size tests measure recognition of one core meaning; they say little about collocations, register or whether you can use the word.
• "Scores from different tests compare directly." Different word lists and counting units make cross-test comparison unreliable.

Sources: Nation, I. S. P., & Beglar, D. (2007). A vocabulary size test. The Language Teacher. Schmitt, N., Schmitt, D., & Clapham, C. (2001). Language Testing. Hu, M., & Nation, I. S. P. (2000). Reading in a Foreign Language. Nation, I. S. P. (2006). Canadian Modern Language Review. Goulden, R., Nation, P., & Read, J. (1990). Applied Linguistics. Brysbaert, M., et al. (2016). Frontiers in Psychology.