How many words does a C1 speaker know?
How many words does a C1 speaker know? Around 3,750 to 4,500 word families, based on Milton and Alexiou's estimates of receptive vocabulary at each CEFR level. C1 is the advanced level: you handle most situations, including work and study, without much strain. That's a well-chosen core, not the whole dictionary. An educated native speaker carries well past 15,000 word families, so C1 is about using a few thousand high-frequency words confidently, not knowing everything. These are receptive counts from one English study measured with a vocabulary-size test, so read the number as a range, not a hard threshold.
The count matters less than which words they are. A small core of very common words does most of the work in real speech, so a C1 speaker gets there by knowing the right words well, not by hoarding rare ones. For the whole table, here's how many words each CEFR level needs.
Source: Milton and Alexiou, vocabulary size across the CEFR levels.
Chasing a big word count is the wrong target. A C1 speaker knows a few thousand words cold, the ones people actually say, and can hear them at speed. That's the skill you're after, not the size of the pile.