Castle Biosciences
Nasdaq • CSTL • US14843C1053
Market Closed
Castle Biosciences
Nasdaq • CSTL • US14843C1053
Market Closed
About this data: CSTL short interest, cost to borrow and days to cover
This page tracks how heavily Castle Biosciences (Nasdaq:CSTL) is being shorted: ORTEX's daily short interest estimate, the cost to borrow the shares, utilization of the lendable supply and days to cover, next to the official exchange-reported figure.
- Short interest
- The number of shares that have been sold short and not yet bought back, usually shown as a percentage of free float (the shares available to trade). ORTEX estimates it every day from securities-lending data, instead of waiting for exchange reports that are published only twice a month and about two weeks late.
- Cost to borrow
- The annualised fee a short seller pays to borrow the shares, as a percentage of the position's value. A rising cost to borrow means lendable shares are getting scarce and holding the short is getting more expensive.
- Utilization
- The share of the lendable supply of a stock that is currently on loan. Close to 100% means almost no shares are left to borrow.
- Days to cover
- Short interest divided by average daily trading volume: roughly how many days of normal trading it would take for every short seller to buy back their shares.
- Exchange-reported short interest
- The official figure published by the exchange or regulator (in the US, FINRA twice a month). It is accurate but delayed, which is the gap the ORTEX daily and intraday estimates fill.
Source: ORTEX. Some figures are limited on the free view; live data and full history are part of ORTEX Advanced.
CSTL key data
Castle Biosciences (Nasdaq: CSTL) has a market capitalization of $982.62M. Last close $33.13 (as of 2026-10-21); 52-week range $17.72 to $44.28. ORTEX data as of 2026-10-19: short interest is 7.27% of free float, 5.4 days to cover and the average cost to borrow is 0.48%.