Core terms
Days to cover
Short interest divided by average daily volume: roughly how many days of normal trading it would take for all short positions to be bought back.
If 2 million shares are short and the stock trades 500,000 shares a day on average, days to cover is 4. The idea is that a higher number means short sellers would need longer to exit, which some traders read as squeeze potential.
Both inputs are imperfect. Short interest is reported with a delay, and average volume changes a lot when a small cap starts moving: one heavy day can turn a days-to-cover of 10 into less than 1.
What traders should verify
Recompute with current volume rather than the figure a screener cached, and keep the short interest date beside it.
Do not conflate
Trader usage; averaging windows differ by source. It is arithmetic on stale data, not a measure of who will buy.
Primary source
Trader usage: there is no official definition, and platforms and tools may calculate it differently.