Short Interest Ratio Calculator
Calculate the short interest ratio (days to cover) from shares sold short and average daily volume.
A high ratio signals elevated short squeeze risk.
Short Interest Ratio (Days to Cover)
The short interest ratio, also called days to cover, measures how many days it would take short sellers to buy back all their borrowed shares at normal trading volume.
Formula:
Short Interest Ratio = Shares Sold Short / Average Daily Volume
| Input | Meaning |
|---|---|
| Shares sold short | The total number of shares currently borrowed and sold by bears |
| Average daily volume | The average number of shares traded per day (typically 10 or 30-day average) |
Short interest as a percentage of float:
Short % of Float = Shares Sold Short / Float Shares
This tells you what fraction of the tradeable shares are being bet against. Above 20% is considered very high.
Read the two numbers together, not separately. They answer different questions and they can disagree sharply. Days to cover asks how long the exit takes; percent of float asks how crowded the trade is. A stock with 40% of its float short but enormous daily volume covers in under a day, so the squeeze risk is genuinely low even though the bearish conviction is extreme. Flip it around and a stock with 8% of float short and almost no volume takes a fortnight to unwind. The calculator below reports both and grades on whichever is more alarming.
When short interest exceeds 100% of float, which sounds impossible and is not: a borrowed share can be sold to a buyer who then lends it out again, so the same share is shorted twice. GameStop reached roughly 140% of float in January 2021. This is the setup with the highest squeeze potential there is, because the shorts collectively cannot close without bidding against each other for shares that do not exist in sufficient number.
Interpreting days to cover:
| Days to Cover | Interpretation |
|---|---|
| Under 1 day | Very low, bears can exit quickly |
| 1 – 3 days | Low, minimal squeeze risk |
| 3 – 5 days | Moderate, watch for catalysts |
| 5 – 10 days | High, meaningful squeeze potential |
| Over 10 days | Very high, significant squeeze risk if stock moves up |
Why it matters:
When a heavily shorted stock rises, short sellers face mounting losses and must eventually buy shares to close their positions. This buying pressure can accelerate the stock’s rise in a feedback loop, which is what a short squeeze is. The days-to-cover ratio tells you how quickly that covering wave could arrive.
Important data note:
FINRA collects short interest from member firms twice a month, on the settlement dates for mid-month and month-end, and publishes it about eight business days later. So the figure you are looking at is typically 7 to 14 days stale before it reaches you. In a fast-moving situation the position can be entirely unwound before the data describing it is published.
Limitations:
High short interest is not automatically bullish. Sometimes the bears have simply read the company correctly, and “heavily shorted” describes plenty of businesses that went on to fail. Many large short positions are not directional bets at all: convertible bond arbitrage, merger arbitrage and index-hedging desks all show up in the same number, and none of them is going to panic-buy on an up day. Combine this with the fundamentals before drawing any conclusion. A squeeze needs a catalyst, and the ratio only tells you how much fuel is lying around.
How we build and check this calculator
This calculator runs entirely in your browser, so the numbers you enter stay on your device. The math behind it is written by hand and tested against worked examples and standard references before the page goes live.
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