About Castle Biosciences, Inc. (CSTL) data
Data as of August 14, 2026.
Castle Biosciences, Inc. (CSTL) has 1.75M shares sold short as of the latest FINRA settlement report on August 14, 2026. Short interest has increased by 12.27% compared with the prior settlement. At the current average daily volume, covering all open short positions would take about 3.68 days (days to cover).
Recent CSTL short interest history
| Settlement date | Short interest | Change | Days to cover |
|---|---|---|---|
| Aug 14, 2026 | 1,753,605 | 12.27% | 3.68 |
| Jul 31, 2026 | 1,561,988 | 9.86% | 3.17 |
| Jul 15, 2026 | 1,421,793 | -4.69% | 5.66 |
| Jun 30, 2026 | 1,491,750 | 0.45% | 3.18 |
| Jun 15, 2026 | 1,485,061 | 0.02% | 5.23 |
| May 29, 2026 | 1,484,771 | 4.88% | 3.78 |
| May 15, 2026 | 1,415,745 | -0.93% | 2.23 |
| Apr 30, 2026 | 1,429,016 | -2.33% | 4.73 |
| Apr 15, 2026 | 1,463,047 | -4.65% | 5.26 |
| Mar 31, 2026 | 1,534,400 | 7.37% | 4.87 |
| Mar 13, 2026 | 1,429,011 | 2.49% | 3.50 |
| Feb 27, 2026 | 1,394,294 | 2.59% | 2.89 |
Full history, charts, and borrow-fee detail are on the CSTL short interest page.
Frequently asked questions
What is the current short interest in CSTL?
As of the latest FINRA settlement dated August 14, 2026, CSTL had approximately 1,753,605 shares sold short. Short interest data is reported by FINRA twice per month.
How much does it cost to short CSTL?
The latest borrow fee (cost to borrow) for CSTL is 0.95% per year, based on IBKR data. Fees can change throughout the trading day as shares are borrowed and returned.
What is the days to cover ratio for CSTL?
Days to cover for CSTL is approximately 3.68 days. This estimates how many trading days it would take short sellers to buy back all outstanding short shares at the current average daily volume.
Is CSTL a short squeeze candidate?
A squeeze needs shorts that are hard to close. CSTL trades about 477,095 shares a day and would take roughly 3.68 days to unwind current short positions, at a current borrow fee of 0.95%. Higher days-to-cover and a rising borrow fee together are the setup to watch; neither alone is enough.