Vocabulary Size of English Speakers

We present the results of an international study on the vocabulary of English speakers. The study is based on an online English vocabulary test, designed for both native speakers and learners. We aimed to answer the following questions:

• How many words do people actually know?
• How does vocabulary size grow with age?
• How large is the difference between the vocabulary sizes of native speakers and learners?

Participants

First, let's look at who took the test. To date, 224,488 respondents have completed it, including 4,099 native speakers and 220,389 English learners. Participants came from all around the world:

More than half of the native speakers (54%) came from the United States, 20% from the United Kingdom, 14% from Canada, and 9% from Australia. Ireland and New Zealand each contributed less than 3% of participants.

Most learners came from Russia (52%) and Ukraine (14%). Each of the remaining countries contributed less than 4% of participants.

The majority of both native speakers and learners were college-age or young adults. However, we still had a broad range of participants, spanning from young children (as young as 5 years old) to older adults (up to 85 years old).

Vocabulary Size

Let's now examine the vocabulary sizes of native speakers and learners.

For native speakers (all ages combined):

• The median vocabulary size is 15,000 word families, meaning half of the native speakers know fewer words, while the other half know more.
• The 25th percentile is 12,500 word families, meaning 25% of native speakers scored below this level, while 75% scored higher.
• The 75th percentile is 17,200 word families, meaning only 25% of native speakers have a larger vocabulary.
• At the 90th percentile, only 10% of native speakers know more than 19,600 word families.

For learners (all ages combined):

• The median vocabulary size is 5,900 word families.
• The 25th percentile is 3,800 word families, meaning 25% of learners scored below this level.
• The 75th percentile is 8,300 word families, meaning only 25% of learners have a larger vocabulary.
• At the 90th percentile, only 10% of learners know more than 10,400 word families.

Vocabulary Size and Age

Now, let's take a closer look at how vocabulary size changes with age. We begin with native speakers:

The vocabulary size of native speakers increases with age. It expands rapidly during formal education (up to age 18), then continues to grow at a slower pace until around 32, after which growth nearly stops. There may be a decline after age 75, but more data is needed to confirm this. Here are the key figures:

• By elementary school graduation (12 years old), a median native speaker knows 10,000 word families.
• By high school graduation (18 years old), vocabulary grows to 13,000 word families.
• A median 22-year-old knows 13,700 word families.
• Most adults (over 35 years old) know, on average, 16,500 word families.
• Students up to 18 years old learn about 600 word families per year.
• Young adults (19–31 years old) acquire around 200 word families per year.
• Later in life (32–75 years old), vocabulary still grows, though more slowly, at about 50 word families per year.

Now, let's look at learners.

For learners:

• The median adult learner (over 35 years old) knows 7,600 word families.
• Half of adult learners (25th–75th percentiles) know between 5,300 and 10,000 word families.
• Only 10% know more than 12,900 word families.

Frequently Asked Questions

How many words are in the English language?

Determining the exact number of words in any language is challenging, as estimates depend on what qualifies as an independent word versus a derivative. We follow the research of P. Nation and L. Bauer, who introduced the concept of word families. According to their work, English has at least 26,000 word families.

What counts as a word?

We measure vocabulary in word families, meaning that variations such as limit, limitation, limitations, limited, limiting, limitless, limitlessly, limits, and unlimited are all considered part of the same word family.

How can a vocabulary of thousands of words be measured with only 40 questions?

The test is based on Item Response Theory and Computerized Adaptive Testing—the most advanced methodologies in modern psychometrics (the science of psychological assessment). You can learn more about the methodology behind the test on the methodology page.

Can I compare these results to those of other vocabulary tests?

Unfortunately, no. Comparing results between vocabulary tests is impossible for several reasons:

• Each test uses different methodologies, measuring slightly different aspects of vocabulary.
• The definition of what counts as a word varies. Some tests include derivative words, while others do not.
• Tests differ in how they define what it means to "know" a word.
• Not all vocabulary tests available online are scientifically rigorous. Only a small fraction are based on validated research methods.

How does the average vocabulary of native English speakers and learners compare to other languages?

Comparing vocabulary sizes across languages is extremely difficult due to fundamental linguistic differences:

• Inflected languages: Some languages, such as Latin, have many inflected forms. For example, the verb amare ("to love") has multiple conjugated forms (amo - "I love", amavi - "I loved", amatus - "loved"). Counting all variations significantly inflates the word count.
• Compound words: In languages like German, long compound words are common. For example, Donaudampfschifffahrtsgesellschaftskapitän ("Danube steamship company captain") is a single word. Whether to count such words separately or as combinations of existing words is debatable.
• Derivational morphology: Some languages, including English, allow extensive word formation through prefixes and suffixes. For example, happy leads to happiness, unhappiness, happily, unhappily. Should these be counted as one word or multiple?
• Loanwords: Many languages borrow words from others. English, for instance, has incorporated words like déjà vu (French), tsunami (Japanese), and emoji (Japanese). Determining when a borrowed word fully integrates into a language adds further complexity.

Thus, meaningful comparisons of vocabulary sizes between languages is practically impossible.

Grigory Golovin

Last updated: March 3, 2025