Definition
Short interest is the amount of a security currently sold short and still open as a short position. Days to cover is commonly calculated as short interest divided by average daily trading volume.
Mechanics
FINRA requires firms to report short interest positions in equity securities on a twice-monthly schedule. The data is useful, but it is delayed and should not be confused with daily short-sale volume.
Worked example
If a stock has 12 million shares sold short and trades 3 million shares per day on average, days to cover is 4. That does not mean every short will cover in four days. It means the open short interest equals roughly four days of average volume.
How to read the signal
| Metric | Useful for | Not useful for |
|---|---|---|
| Short interest | Identifying open short positioning. | Precise real-time exposure. |
| Days to cover | Estimating crowding relative to liquidity. | Predicting exact squeeze timing. |
| Short-sale volume | Understanding transaction flow. | Replacing position data. |
Common mistakes
- Treating short interest as a standalone buy or sell signal.
- Ignoring delayed publication timing.
- Confusing high short interest with a weak company.
- Ignoring float, borrow fees, options positioning, and catalyst timing.
Stock Shorter framing
Stock Shorter uses short interest as a structure filter, not a thesis generator. AI-disruption evidence can identify vulnerable companies, but short interest and days to cover help determine whether a direct short, put spread, basket, or pairs trade is more appropriate.
This page is educational research, not investment advice or a recommendation.