What is the Repo Rate? Definition, Formula, and Example
The repo rate is the interest rate charged on a repurchase agreement, an overnight loan collateralized by securities, and it's the plumbing rate that keeps short-term bank funding markets liquid.
What is the Repo Rate?
The repo rate is the interest rate paid on a repurchase agreement — a transaction where one party sells securities (almost always Treasuries) to another with an agreement to buy them back the next day (or after a set term) at a slightly higher price. Economically it's a secured, short-term loan: the cash borrower posts Treasuries as collateral, and the difference between the sale price and the repurchase price is the interest. The repo market is where banks, dealers, money-market funds, and hedge funds source and lend overnight cash by the trillions of dollars daily, and the rate that clears that market is one of the most important — and least visible to retail — interest rates in the financial system.
How It's Calculated
Repo interest = Principal × Repo rate × (Days / 360)
For an overnight repo, days = 1. The repo rate itself is simply the annualized cost implied by the difference between the sale and repurchase price:
Repo rate = [(Repurchase price − Sale price) / Sale price] × (360 / Days)
The benchmark reference for the U.S. repo market is SOFR (Secured Overnight Financing Rate), published daily by the New York Fed from actual overnight Treasury repo transaction data. As of early July 2026, SOFR sits at roughly 3.62%. SOFR replaced LIBOR as the standard short-term dollar reference rate because it's derived from real, observable transactions rather than a bank survey.
Worked Example
A dealer needs $100 million in overnight cash and repos out Treasuries at a rate of 3.62%. Using the formula: interest = $100,000,000 × 0.0362 × (1/360) = $10,055.56 for that one night. The dealer repurchases the same securities the next day for $100,010,055.56.
The most dramatic real-world example of repo rates breaking is September 17, 2019, when a confluence of large Treasury settlements, corporate tax payments, and a multiyear low in bank reserves caused overnight repo rates to spike from 2.43% to 5.25% — and as high as 10% intraday — as cash lenders suddenly demanded a much higher rate to part with liquidity. The New York Fed responded by injecting $75 billion in overnight liquidity daily for the rest of that week, and rates normalized to roughly 1.75-1.9% within three trading days.
When Traders Use It
Repo rates matter to traders in three ways. First, as a plumbing gauge: a repo rate that spikes above the Fed's target range signals a cash shortage in the banking system, historically a precursor to Fed liquidity operations or, in extreme cases, broader market stress. Second, as a funding cost: leveraged strategies like the basis trade and carry trade borrow in the repo market to finance positions, so the repo rate directly determines the profitability of the spread being captured. Third, as a Fed-policy signal: the Fed sets an overnight reverse repo (ON RRP) rate as a floor for short-term rates, and persistent deviations from that floor tell traders about reserve scarcity in the system well before it shows up in equity or credit markets.
Limitations and Common Misconceptions
The repo rate is not a single number — there are general collateral (GC) repo rates, specials rates (when a particular security is in high demand and trades at a lower — sometimes negative — rate), and rates that vary by term and collateral type. SOFR is a broad average and can mask specials trading well below it. It's also a lagging, backward-looking print (published the next morning based on the prior day's transactions), so it confirms stress after the fact rather than predicting it. Finally, a repo rate spike is a funding-market event, not automatically a solvency or equity-market event — the September 2019 episode caused no equity selloff, even though it forced an emergency Fed response.