What short interest percentage is considered high?

No official cutoff exists, and traders draw the line in different places. The percentage means more when read alongside days to cover and borrow cost. A stock with high short interest and heavy daily volume can absorb buybacks easily; the same short interest in a thinly traded stock is far more fragile.

How often is short interest updated?

FINRA gathers short positions from broker-dealers twice a month and publishes the figures after each collection date, so any number on a quote page describes positions from days or weeks earlier. Squeezes can start and finish between two reports. Check the settlement date shown next to the figure to see how old it is.

Short Squeeze: Short Interest, Days to Cover and How One Starts

Short interest: 12,000,000 shares. Float: 60,000,000. Average volume: 2,000,000. Those lines sit on a quote page, usually tucked below the price and the market cap, and between them they say how many people are betting against the stock and how long it would take them all to get out.

Short interest against float, and days to cover

Short interest as a share of float compares the shares sold short with the shares available to trade. Days to cover divides the shares sold short by average daily volume, which gives a rough count of how many full days of normal trading it would take for every short seller to buy back.

A fifth of the tradable shares are sold short. If every short tried to buy back at once, they would need six days of the stock’s entire normal volume to do it, and they would be competing with every other buyer the whole time.

How a squeeze starts

A short seller borrows shares, sells them, and hopes to buy them back cheaper. The loss on a short has no ceiling. If the price rises, the short is losing money, and at some point a margin call, a stop order or plain discomfort forces a buyback.

That buyback is a buy order. In a heavily shorted stock, a rise on good news triggers the first round of covering, which pushes the price up, which puts the next group of shorts under water, whose stops fire and push the price up again, and the loop keeps going until the shorts who had to cover have covered or the rise attracts enough sellers to absorb them. The rally feeds itself for a while.

Most squeezes need a spark. Earnings above expectations, a takeover rumor or a sudden break above a level everyone was watching can all do it. Short interest is only the fuel.

How it shows up on a quote page

Most quote pages show short interest as a share count, a percentage of float, or both, often with days to cover next to it and a date. That date is the one to read first.

Some pages also list a borrow fee or a hard-to-borrow flag. A high fee means shares for shorting are scarce. Shorts also pay it every day they hold. That raises the pressure to close.

Why it matters to a short swing trader

If you are the one short, the squeeze is the risk. A crowded short can gap through a stop overnight. A stop at $50 does nothing when the stock opens at $56 on news; it fills near $56, and the loss is larger than the one you planned for. High short interest, a long days-to-cover figure and rising borrow fees together are the conditions under which that happens most readily.

That’s why rules for shorting usually include a screen for crowding. Swing trading the short side sets out one version, and traders who want bearish exposure without borrowing single stocks look at the funds in short swing trading ETFs, where squeeze risk in the single-stock sense does not apply.

What people get wrong

Buying a stock only because short interest is high is the common one. Heavily shorted stocks are often shorted for a reason, and many drift lower for months without any squeeze. A second is reading a stale short interest figure as current. A third is treating days to cover as exact: average volume changes, and on a squeeze day volume can run many times the average, so shorts can cover faster than the number suggests.

Float, borrow fee, hard to borrow, margin call and gap risk. Places to look up short interest and the reporting calendar are gathered in trader resources. More on trading from the short side sits under the swing trading topic.