About 6.87M shares of Spero Therapeutics Inc are sold short, or roughly 2.46% of the float. At recent volume that works out to about 1.00 days to cover, with a borrow fee near 70.80% and a squeeze score of 27.0 out of 100. No single number tells you whether a squeeze is coming, so it helps to read the whole picture below.
This page gathers everything we track on the short side of Spero Therapeutics Inc (SPRO) in one place, ordered by how quickly each number changes. The fastest moving figures, like the borrow fee, sit near the top. Daily figures such as short volume and fails to deliver come next. The slowest data, the official short interest that exchanges publish twice a month, sits at the bottom. Reading it top to bottom gives you a feel for what is happening right now versus what has built up over time.
Where the numbers come from. Short interest and short volume are reported by the exchanges and FINRA rather than any single broker, so they reflect trading across the whole market. Float and shares outstanding come from a separate data provider on their own schedule, which is why the percentages can shift even when the raw short interest has not changed.
Is short interest reliable? It is not something a company reports about itself. Brokerages are required to report their open short positions to FINRA twice a month, once around the middle of the month and once at the end, so the figure is a real settlement number rather than an estimate.
What about dark pool trades? They are included. A trade executed in a dark pool still prints to the tape and settles like any other trade, so any short position it creates is counted at the next settlement date no matter where the shares changed hands.
SPRO scores 27 out of 100. The biggest factor is borrow fee at 70.8% (high); days to cover of 1.00 is low and a borrow fee near 70.8% is high. Short-side pressure is middling and nothing here points to an imminent squeeze.
A relative reading versus other stocks, not a prediction. It weighs short interest, float, days to cover and the cost to borrow into one 0–100 number where 50 is the middle of the pack.
Reported short interest for SPRO at each date, shown with days to cover and short interest as a percent of float. Short interest updates twice a month; the percentages are recomputed as float changes.
| Date | Short Interest | Days to Cover | SI % Float | Float (MM) | Shares Out (MM) |
|---|---|---|---|---|---|
| 2026-05-17 | — | — | 2.46% | 47.34 | 57.90 |
| 2026-05-16 | — | — | 2.46% | 47.34 | 57.90 |
| 2026-05-15 | — | — | 2.46% | 47.33 | 57.90 |
| 2026-05-14 | — | — | 2.46% | 47.33 | 57.90 |
The raw short interest NASDAQ publishes at each settlement date, with the publication date and the change from the prior period. These are the exchange own figures and are not adjusted for stock splits.
| Settlement Date | Publication Date | Short Interest | Percent Change | SI Ratio (DTC) | Float (MM) | SI % Float |
|---|---|---|---|---|---|---|
| 2026-07-19 | 2026-07-29 | 6,874,599 | 0.00% | 1.33 | 44.66 | 15.39 |
| 2026-07-04 | 2026-07-14 | 6,236,081 | 9.29% | 2.07 | 52.76 | 11.82 |
| 2026-06-19 | 2026-06-29 | 6,388,005 | -2.44% | 1.76 | 45.19 | 14.14 |
| 2026-06-04 | 2026-06-14 | 5,696,642 | 10.82% | 1.07 | 45.72 | 12.46 |
| 2026-05-20 | 2026-05-30 | 6,333,052 | -11.17% | 1.62 | 43.18 | 14.67 |
| 2026-05-05 | 2026-05-15 | 5,445,010 | 14.02% | 1.47 | 53.36 | 10.20 |
| 2026-04-20 | 2026-04-30 | 4,722,517 | 13.27% | 1.15 | 44.95 | 10.51 |
| 2026-04-05 | 2026-04-15 | 5,260,746 | -11.40% | 1.22 | 51.21 | 10.27 |
| 2026-03-21 | 2026-03-31 | 5,584,558 | -6.16% | 0.87 | 54.72 | 10.21 |
| 2026-03-06 | 2026-03-16 | 4,801,998 | 14.01% | 1.27 | 56.25 | 8.54 |
| 2026-02-19 | 2026-03-01 | 4,834,529 | -0.68% | 1.38 | 46.64 | 10.37 |
| 2026-02-04 | 2026-02-14 | 4,360,094 | 9.81% | 1.55 | 44.02 | 9.90 |
How many SPRO shares were sold short off exchange each day, summed across the reporting venues we track. It includes market maker hedging and other routine activity, so a high reading is normal and is not the same as outstanding short interest.
| Market Date | Non-Exempt Vol | Exempt Vol | Short Vol | Total Vol | Short Vol Ratio |
|---|---|---|---|---|---|
| 2026-07-27 | 970 | 0 | 970 | 2,794 | 34.7% |
| 2026-07-24 | 939,076 | 160,852 | 1,099,928 | 4,828,137 | 22.8% |
| 2026-07-23 | 469,886 | 6,900 | 476,786 | 2,281,725 | 20.9% |
| 2026-07-22 | 405,135 | 20,418 | 425,553 | 2,355,583 | 18.1% |
| 2026-07-21 | 150,667 | 12,596 | 163,263 | 926,879 | 17.6% |
| 2026-07-20 | 361,422 | 10,436 | 371,858 | 1,895,525 | 19.6% |
| 2026-07-17 | 136,533 | 4,754 | 141,287 | 616,835 | 22.9% |
| 2026-07-16 | 376,365 | 47,730 | 424,095 | 2,205,749 | 19.2% |
| 2026-07-15 | 213,246 | 21,800 | 235,046 | 1,362,936 | 17.2% |
| 2026-07-14 | 3,525,920 | 315,229 | 3,841,149 | 9,849,857 | 39.0% |
| 2026-07-13 | 325,301 | 6,002 | 331,303 | 592,486 | 55.9% |
| 2026-07-10 | 162,765 | 0 | 162,765 | 241,697 | 67.3% |
| 2026-07-09 | 76,318 | 953 | 77,271 | 176,744 | 43.7% |
| 2026-07-08 | 105,698 | 0 | 105,698 | 226,826 | 46.6% |
| 2026-07-07 | 244,674 | 8 | 244,682 | 1,047,810 | 23.4% |
| 2026-07-06 | 71,407 | 128 | 71,535 | 135,640 | 52.7% |
| 2026-07-02 | 249,198 | 2,946 | 252,144 | 530,466 | 47.5% |
| 2026-07-01 | 119,182 | 6 | 119,188 | 324,117 | 36.8% |
| 2026-06-30 | 330,657 | 24 | 330,681 | 468,953 | 70.5% |
| 2026-06-29 | 308,347 | 1,360 | 309,707 | 509,909 | 60.7% |
| 2026-06-26 | 805,041 | 3,362 | 808,403 | 1,533,649 | 52.7% |
| 2026-06-25 | 565,423 | 1,148 | 566,571 | 1,368,555 | 41.4% |
| 2026-06-24 | 407,316 | 0 | 407,316 | 927,716 | 43.9% |
| 2026-06-23 | 292,278 | 0 | 292,278 | 613,130 | 47.7% |
| 2026-06-22 | 1,046,013 | 54,288 | 1,100,301 | 2,126,338 | 51.7% |
| 2026-06-18 | 2,634,487 | 248,346 | 2,882,833 | 4,766,300 | 60.5% |
| 2026-06-17 | 5,449,072 | 350,252 | 5,799,324 | 10,427,888 | 55.6% |
| 2026-06-16 | 861,682 | 1,464 | 863,146 | 1,156,677 | 74.6% |
| 2026-06-15 | 614,359 | 1,140 | 615,499 | 1,042,670 | 59.0% |
| 2026-06-12 | 258,320 | 0 | 258,320 | 577,208 | 44.8% |
Off-exchange volume combined with the on-exchange venues we track. The aggregate columns cover those venues only, not every place SPRO trades, so treat the totals as a representative sample rather than a full market count.
| Market Date | FINRA Short | PSX/BX Short | Aggregate Short | Aggregate Total | Agg Short Ratio |
|---|---|---|---|---|---|
| 2026-07-29 | 5,743,046 | 7,834 | 5,750,880 | 9,552,960 | 60.2% |
| 2026-07-28 | 5,707,810 | 23,996 | 5,731,806 | 11,295,234 | 50.7% |
| 2026-07-27 | 3,121,993 | 38,171 | 3,160,164 | 5,104,545 | 61.9% |
| 2026-07-24 | 5,302,781 | 81,073 | 5,383,854 | 10,224,000 | 52.7% |
| 2026-07-23 | 3,659,820 | 53,288 | 3,713,108 | 7,084,901 | 52.4% |
| 2026-07-22 | 3,148,933 | 11,754 | 3,160,687 | 5,338,704 | 59.2% |
| 2026-07-21 | 2,543,794 | 42,556 | 2,586,350 | 5,157,858 | 50.1% |
| 2026-07-20 | 2,843,155 | 11,975 | 2,855,130 | 5,682,030 | 50.2% |
| 2026-07-17 | 3,279,260 | 25,533 | 3,304,793 | 5,333,901 | 62.0% |
| 2026-07-16 | 5,355,586 | 30,624 | 5,386,210 | 9,646,802 | 55.8% |
SPRO shares that did not settle on time, reported by the SEC. Each figure is a running balance on a given date rather than a daily tally, and it is not added up across dates. Fails happen for many ordinary reasons and are not on their own a sign of anything improper.
| Settlement Date | Price | Quantity | Value |
|---|---|---|---|
| 2026-06-30 | $2.26 | 47,602 | $107,580.52 |
| 2026-06-29 | $2.26 | 730 | $1,649.80 |
| 2026-06-24 | $2.15 | 1,011 | $2,173.65 |
| 2026-06-22 | $2.28 | 9,572 | $21,824.16 |
| 2026-06-18 | $2.11 | 3,755 | $7,923.05 |
| 2026-06-17 | $2.77 | 20,293 | $56,211.61 |
| 2026-06-16 | $2.91 | 5,631 | $16,386.21 |
| 2026-06-15 | $2.85 | 23,494 | $66,957.90 |
| 2026-06-12 | $2.70 | 5,678 | $15,330.60 |
| 2026-06-11 | $2.54 | 15,911 | $40,413.94 |
| 2026-06-08 | $2.82 | 11,224 | $31,651.68 |
| 2026-05-29 | $2.90 | 16,734 | $48,528.60 |
| 2026-05-28 | $2.93 | 899 | $2,634.07 |
| 2026-05-27 | $2.86 | 3,886 | $11,113.96 |
| 2026-05-19 | $2.58 | 36,410 | $93,937.80 |
| 2026-05-18 | $2.79 | 300 | $837.00 |
| 2026-05-15 | $2.76 | 300 | $828.00 |
| 2026-04-23 | $2.86 | 1,848 | $5,285.28 |
| 2026-04-20 | $2.75 | 2,400 | $6,600.00 |
| 2026-04-14 | $2.78 | 2,710 | $7,533.80 |
| 2026-04-10 | $2.78 | 2,328 | $6,471.84 |
| 2026-04-08 | $2.67 | 219 | $584.73 |
| 2026-03-12 | $2.59 | 943 | $2,442.37 |
| 2026-02-26 | $2.22 | 2,579 | $5,725.38 |
How many SPRO shares one large prime broker had available to lend at each timestamp. It is a sample of a single lender, not the total shortable pool and not the short interest, but the direction over a day or two is a useful read on demand. Last update 7 minutes ago.
| Time Since Last Change | Timestamp (UTC) | SPRO Short Shares Availability |
|---|---|---|
| 42 minutes ago | 2026-07-29 00:00 UTC | 200,000 |
| 2 hours ago | 2026-07-28 23:07 UTC | 150,000 |
| 6 hours ago | 2026-07-28 19:14 UTC | 100,000 |
| 6 hours ago | 2026-07-28 19:21 UTC | 150,000 |
| 7 hours ago | 2026-07-28 18:28 UTC | 200,000 |
| 8 hours ago | 2026-07-28 17:35 UTC | 250,000 |
| 11 hours ago | 2026-07-28 14:42 UTC | 700 |
| 15 hours ago | 2026-07-28 10:49 UTC | 900 |
| 17 hours ago | 2026-07-28 08:56 UTC | 500 |
| 20 hours ago | 2026-07-28 05:03 UTC | 400 |
The annualized rate a short seller pays to borrow SPRO. The latest reading is 70.80%. A high or rising fee means shares are getting harder and more expensive to short, which is one of the conditions that can feed a squeeze.
| Date | Borrow Fee |
|---|---|
| 2026-07-28 | 70.80% |
| 2026-07-27 | 71.93% |
| 2026-07-24 | 73.90% |
| 2026-07-23 | 74.35% |
| 2026-07-22 | 74.92% |
| 2026-06-08 | 53.92% |
| 2026-06-05 | 52.98% |
| 2026-06-04 | 52.40% |
| 2026-06-03 | 52.82% |
| 2026-06-02 | 52.62% |
| 2026-06-01 | 52.38% |
| 2026-05-29 | 52.07% |
| 2026-05-28 | 52.02% |
| 2026-05-27 | 51.87% |
| 2026-05-26 | 51.39% |
| 2026-05-25 | 51.44% |
| 2026-05-22 | 51.67% |
| 2026-05-21 | 51.88% |
| 2026-05-20 | 52.15% |
| 2026-05-19 | 52.32% |
| 2026-05-18 | 52.37% |
| 2026-05-15 | 52.57% |
| 2026-05-14 | 52.61% |
| 2026-05-13 | 52.72% |
