What Is Short Interest? Days to Cover and Squeeze Risk (2026)

What short interest counts

A short seller borrows shares, sells them, and later buys shares back to return to the lender. Until that purchase, the position is open. Short interest is the sum of those open positions in one stock.

FINRA Rule 4560 requires member firms to report short positions in all customer and proprietary accounts in equity securities. FINRA describes the result as a snapshot of open short positions on firms' books on a given settlement date. Two features of that definition matter:

• It is a snapshot. It shows positions at the close of two days a month. Shorts opened and closed between those dates never appear.
• It is positions, not trades. A short sale closed the same day shows up in daily short sale volume but not in short interest. A short held for months shows up in every report while it stays open.

FINRA's data file reports the current short position, the previous cycle's short position, average daily volume and days to cover for each security. It does not report float. Percent-of-float figures come from data providers that combine FINRA's number with their own float estimate.

The 2026 reporting calendar

The mid-month settlement date is the 15th, or the prior day that settles if the 15th falls on a weekend or holiday. The end-of-month date is the last business day of the month on which trades settle. Firms must report by 6 p.m. Eastern on the second business day after each settlement date, and FINRA publishes on the seventh business day.

FINRA's published schedule for the rest of 2026:

The lag is the point to remember. A figure published on October 26 describes positions as of October 15. If a company reports earnings on October 22, no official short interest figure taken after the report will exist until November 10.

Days to cover and short interest as a percent of float

Two ratios turn the raw share count into something you can compare across companies.

Days to cover is short interest divided by average daily share volume. FINRA's glossary sets the formula as short interest divided by average daily share volume, rounded to hundredths. Its average daily volume covers the trading days from the day after the previous settlement date through the current one, roughly two weeks. FINRA shows 1.00 for any value at or below one, and N/A when volume is zero.

Many websites use a 30-day or longer volume average instead. A stock that traded heavily on one news day will show a lower days-to-cover figure on a site whose window includes that day. Before comparing two sources, check which window each uses.

Short interest as a percent of float is short interest divided by the shares available to trade, which excludes shares held by insiders and other locked-up holders. Float is an estimate, and providers disagree about it. A company with a large insider stake, or with shares about to come out of a lockup, can show very different percentages from one site to the next.

The two ratios answer different questions. Percent of float shows how crowded the short side is. Days to cover shows how hard it would be to leave. A stock can be heavily shorted as a share of float yet trade so much volume that shorts could exit in a day or two.

A worked example

The arithmetic:

1. Percent of float: 7 million divided by 28 million is 25%.
2. Percent of shares outstanding: 7 million divided by 40 million is 17.5%. Some sites quote this figure instead, which is why the same stock can look less crowded on one page than on another.
3. Days to cover: 7 million divided by 700,000 is 10.00.
4. Change: short interest rose 1.5 million shares, or about 27%, between reports.

Now suppose Company A has a court ruling on a patent case scheduled in three weeks, and a sizable part of the short position is likely a bet on an adverse ruling. If the ruling goes the company's way, holders of 7 million short shares may want to buy at once, in a stock that normally trades 700,000 a day. That is the setup squeeze discussions describe.

It is still only a setup. Some of the 7 million may be hedges against convertible bonds or long positions in a related company, and those holders have no reason to cover on the ruling. Some may have covered since the settlement date. The official figure cannot show either.

What turns short interest into squeeze risk

A short squeeze is a feedback loop: short sellers buy to close, their buying lifts the price, and the higher price forces more short sellers to buy. A high short interest figure is one input. The loop needs several conditions at once.

• A crowded, slow exit. High percent of float together with high days to cover. Either one alone is weaker.
• A dated trigger. An earnings report, a ruling, a vote, a tender offer or another catalyst that can change the thesis behind the short in one day.
• Rising cost to borrow. When lendable shares run short, borrow fees rise and lenders may recall shares. A short who must pay a high daily fee, or return shares on short notice, has less patience. Borrow data comes from securities lending sources, not from FINRA's short interest file.
• Options positioning. Heavy buying of out-of-the-money calls can lead option dealers to buy stock as a hedge, which adds to buying pressure as the price rises. Open interest by strike and implied volatility show whether that positioning exists.
• Thin supply of sellers. Large insider or locked-up holdings shrink the pool of shares that can meet covering demand.

A quick way to sort a stock:

• If short interest is high but days to cover is under two, shorts can likely exit without moving the price much.
• If days to cover is high but there is no dated event in the next few weeks, the position can sit for months without forcing anyone's hand.
• If short interest is rising into a dated event, days to cover is high and borrow costs are climbing, the stock has the ingredients, and the event outcome decides whether they matter.
• If short interest is falling sharply before the event, shorts may already be leaving, and the squeeze case has weakened.

How to read short interest before a catalyst

Put the dates first. Find the event on your catalyst calendar, then find the last FINRA settlement date before it and the publication date that follows. You will know exactly how stale your number will be on the event day.

Then read the trend, not the level. Three or four consecutive reports show whether shorts are building, holding or leaving. A single report can be distorted by one large fund or by a hedge tied to a convertible issue.

Compare the stock side with the options side. Short interest, open interest by strike and the implied move priced by the straddle on the first expiry after the event describe the same positioning from different angles. Our guide on estimating an earnings move from options covers that last step.

Dombey's weekly Options Research reviews short positioning next to options data before dated catalysts; see the research archive.

Where this goes wrong

Reading the number as current. The official figure is at least nine calendar days old when it is published and can be more than three weeks old before the next one replaces it. Estimates from lending data fill the gap but are estimates.

Mixing sources. Short interest from one site, float from another and volume from a third can produce a days-to-cover figure that matches nothing. Use one source's numbers together, or rebuild the ratio yourself from FINRA's file.

Assuming every short is a bet against the company. Merger arbitrage funds short the acquirer in stock deals. Convertible bond holders short the stock as a hedge. Market makers carry short positions from ordinary trading. None of these holders will rush to cover because the stock rises.

Confusing short volume with short interest. FINRA states that daily short sale volume and short interest are not the same. A day when half of reported volume was short sales says little about open positions.

Treating high short interest as a buy signal. Heavily shorted companies are sometimes shorted for good reasons: weak cash flow, dilution risk or accounting questions. A crowded short can be right.

The bottom line

Short interest is the count of shares sold short and still open, reported twice a month and published by FINRA on the seventh business day after each settlement date. Days to cover and percent of float turn it into a measure of how crowded and how hard to exit the short side is. Squeeze risk becomes real only when a crowded, slow-to-exit short meets a dated event, rising borrow costs and supportive options positioning. Read the trend, check the dates against your catalyst, and treat the number as a description of past positioning. This article is education, not a recommendation to trade any security.