What is a Stock Borrow Rate? Definition, Formula, and Example
A stock borrow rate is the annualized interest fee a broker charges a short seller for locating and borrowing shares of a specific stock to facilitate a short sale.
What is a Stock Borrow Rate?
A stock borrow rate is the annualized percentage fee a short seller pays to a brokerage or clearing firm to borrow shares of a stock required to execute a short sale. Because short selling requires delivering shares the trader does not own, the trader must borrow them from the broker's inventory or a third-party lender. The borrow rate fluctuates daily based on the supply of lendable shares and the demand from short sellers. When a stock becomes heavily shorted or experiences a liquidity squeeze, the borrow rate spikes to reflect the scarcity of available shares.
How the Stock Borrow Rate is Calculated
The daily cost of holding a short position is derived from the annualized borrow rate applied to the total notional value of the shorted shares. The formulas are:
Notional Value = Current Share Price × Number of Shorted Shares
Daily Borrow Fee = (Notional Value × Annualized Borrow Rate) / 360
Brokers quote two distinct rates:
1. General Collateral (GC) Rate: The baseline rate (often tied to the Fed Funds Rate, e.g., 0.25% to 5%) applied to highly liquid stocks with ample supply.
2. Hard-to-Borrow (HTB) Rate: A specialized, elevated rate applied to stocks with restricted share supply, which can range from 10% to over 100% annually.
The broker calculates the fee daily and deducts it directly from the trader's account margin at the end of each trading day.
Worked Example
Assume a trader shorts 10,000 shares of GME at $20.00 per share. Due to high short interest, the broker designates GME as a hard-to-borrow stock and charges an annualized borrow rate of 50%.
- Notional Value: $20.00 × 10,000 = $200,000
- Annual Borrow Fee: $200,000 × 0.50 = $100,000
- Daily Borrow Fee: $100,000 / 360 = $277.77
The trader is charged $277.77 every day they maintain the short position. If the trader holds the position for 30 days, the total borrow cost exceeds $8,300. This daily drag on equity means the stock must fall by more than $0.83 per share just for the trader to break even on the short sale, excluding commissions and dividend obligations.
When Traders Use It
Traders evaluate the stock borrow rate before initiating a short sale to calculate the precise cost of carry. A high borrow rate forces short sellers to achieve a larger percentage decline in the stock price just to overcome the daily interest drag. Arbitrageurs and statistical traders monitor borrow rates to identify short squeezes; a sudden spike in the HTB rate signals that share supply is tightening, which can precede a rapid forced buy-in by brokers. Long-biased traders also monitor borrow rates to gauge the fragility of the short seller base, using extreme rates as a contrarian signal to buy shares.
Limitations and Common Misconceptions
The stock borrow rate is not static; a broker can change the rate intraday without warning if the clearing firm fails to locate additional shares. A common misconception is that shorting a stock is free if the trader holds the position for only a few minutes; in reality, clearing firms calculate borrow fees on a daily settlement cycle, meaning even overnight holds incur costs. Furthermore, a high borrow rate does not guarantee a short squeeze will occur. If the underlying company continuously dilutes its share count, the supply of borrowable shares increases, collapsing the borrow rate and trapping short sellers who priced in a squeeze based on scarcity alone.