Treasury bill rates over the past year, auction by auction
Every bill auction since September 2025, averaged by month for four terms, with the highest and lowest rate of each. The 13-week bill went from 3.999 % to 4.185 %.
13-week bill, auction of October 13, 2026
4.185 %
Investment rate (bond-equivalent yield). You pay $9,896.74 and receive $10,000 on January 14, 2027.
| Discount rate | 4.085 % |
| Price per $100 | 98.967403 |
| Interest at maturity | $103.26 |
| Days to maturity | 91 |
| Issue date | October 15, 2026 |
| Term | Auction | Discount | Investment rate | Price per $100 |
|---|---|---|---|---|
| 4-week | October 15, 2026 | 4.000 % | 4.068 % | 99.688889 |
| 6-week | October 13, 2026 | 3.980 % | 4.055 % | 99.524611 |
| 8-week | October 15, 2026 | 4.050 % | 4.132 % | 99.37 |
| 13-week | October 13, 2026 | 4.085 % | 4.185 % | 98.967403 |
| 17-week | October 14, 2026 | 4.195 % | 4.313 % | 98.613319 |
| 26-week | October 13, 2026 | 4.200 % | 4.351 % | 97.876667 |
| 52-week | September 29, 2026 | 4.400 % | 4.616 % | 95.551111 |
Worked out by Radif Partners · How we calculate · rates read on treasurydirect.gov and fiscaldata.treasury.gov · not personal financial advice
Treasury bill rates are set at each auction, so a rate history is a list of auction results. Over the 57 auctions of the 13-week bill from September 15, 2025 to October 13, 2026, the investment rate moved from 3.999 % to 4.185 %, with a low of 3.622 % on January 5, 2026 and a high of 4.211 % on September 28, 2026. The 26-week bill ended the period higher by 0.512 %, the 4-week bill lower by 0.041 %. The 52-week bill, sold only every four weeks, went from 3.688 % to 4.616 %. The table below averages the auctions of each month; the second table gives each term's range. These are investment rates, the yield on the price paid, computed by the Treasury and published on Fiscal Data. Past auction rates say nothing certain about the next auction.
Average investment rate by month
| Month | 4-week | 13-week | 26-week | 52-week |
|---|---|---|---|---|
| October 2026 | 4.024 % | 4.167 % | 4.332 % | |
| September 2026 | 3.850 % | 4.070 % | 4.243 % | 4.388 % |
| August 2026 | 3.700 % | 3.825 % | 3.958 % | 4.054 % |
| July 2026 | 3.712 % | 3.849 % | 4.000 % | 4.032 % |
| June 2026 | 3.660 % | 3.755 % | 3.868 % | 3.914 % |
| May 2026 | 3.674 % | 3.688 % | 3.741 % | 3.806 % |
| April 2026 | 3.654 % | 3.698 % | 3.719 % | 3.710 % |
| March 2026 | 3.690 % | 3.700 % | 3.691 % | 3.630 % |
| February 2026 | 3.689 % | 3.681 % | 3.626 % | 3.480 % |
| January 2026 | 3.661 % | 3.653 % | 3.615 % | 3.528 % |
| December 2025 | 3.666 % | 3.697 % | 3.653 % | 3.517 % |
| November 2025 | 3.958 % | 3.873 % | 3.815 % | 3.603 % |
| October 2025 | 4.063 % | 3.899 % | 3.792 % | 3.587 % |
| September 2025 | 4.130 % | 3.968 % | 3.835 % | 3.688 % |
A month's figure for the 13-week bill is the mean of four or five weekly auctions, so it smooths the week-to-week moves that the auction results themselves show. The calculator at the top gives the exact result of the latest auction of any term.
Range of each term over the period
| Term | Auctions | Lowest | Highest | Latest |
|---|---|---|---|---|
| 4-week | 57 | 3.609 % (January 8, 2026) | 4.150 % (September 25, 2025) | 4.068 % |
| 13-week | 57 | 3.622 % (January 5, 2026) | 4.211 % (September 28, 2026) | 4.185 % |
| 26-week | 57 | 3.586 % (January 5, 2026) | 4.441 % (September 28, 2026) | 4.351 % |
| 52-week | 14 | 3.480 % (February 17, 2026) | 4.616 % (September 29, 2026) | 4.616 % |
The range of a term over a year is the most direct measure of how much a saver who rolls bills can expect the rate to move. On the 13-week bill the gap between the lowest and the highest auction of the period was 0.589 %. On $100,000 kept in 13-week bills for a year, a shift of that size changes the interest by about $589 a year.
Cost and interest at the latest 13-week auction
13-week bill, auction of October 13, 2026
4.185 %
| Discount rate | 4.085 % |
| Price per $100 | 98.967403 |
| Interest at maturity | $516.30 |
| Days to maturity | 91 |
Short bills against the one-year bill
The difference between the 52-week and the 4-week rate shows how the market priced a one-year commitment against a one-month one. In September 2025 the 52-week bill paid 0.442 % less than the 4-week bill; in September 2026, 0.538 % more. When the one-year rate is below the one-month rate, buyers are accepting less for a longer lock, which usually means they expect short rates to fall; when it is above, the reverse. Each figure is one auction's price and moves with the next one.
For someone choosing a term, that spread is the price of certainty. A 52-week bill fixes the rate for a year; a 4-week bill rolled twelve times takes twelve different rates. The latest T-bill rates page shows today's spread, and the T-bill calculator turns any rate into a price.
Four quarters of 13-week bills against one 52-week bill
Rolling bills means reinvesting at each maturity at the new auction's rate. The table follows $10,000 put into the 13-week bill at the first auction of the period and rolled three times, every 13 weeks, with the whole proceeds reinvested at each auction's discount rate. Fractions of $100 would in practice stay in cash; the table keeps them invested to show the rate effect alone.
| Auction | Investment rate | Invested | Paid at maturity |
|---|---|---|---|
| September 15, 2025 | 3.999 % | $10,000.00 | $10,099.69 |
| December 15, 2025 | 3.642 % | $10,099.69 | $10,191.40 |
| March 16, 2026 | 3.694 % | $10,191.40 | $10,285.26 |
| June 15, 2026 | 3.725 % | $10,285.26 | $10,380.77 |
Over the four quarters the rolled bills earned $380.77. A single 52-week bill bought at the auction of September 30, 2025, at 3.688 %, would have earned about $371.22 on the same $10,000 over its 364 days. The difference is the cost or the reward of keeping the rate open, and it changes sign from one year to the next.
The 6, 8 and 17-week bills
The other three regular terms follow the same pattern with their own levels. The 6-week bill went from 4.116 % on September 16, 2025 to 4.055 % on October 13, 2026, within a range of 3.624 % to 4.116 %. The 8-week bill went from 4.045 % on September 18, 2025 to 4.132 % on October 15, 2026, within a range of 3.609 % to 4.132 %. The 17-week bill went from 3.917 % on September 17, 2025 to 4.313 % on October 14, 2026, within a range of 3.601 % to 4.313 %. Having seven terms lets a buyer pick a maturity close to the date the money is needed, which matters more than a few hundredths of a percent when the money is meant for a known expense.
How the figures are built
The site downloads every regular bill auction from the Fiscal Data auctions dataset (Fiscal Data): the 4, 6, 8, 13, 17, 26 and 52-week bills, without cash management bills, which are sold only through banks and dealers at irregular dates (TreasuryDirect). Reopenings, when the Treasury sells more of an existing bill, count as auctions of their own. The investment rate is the one the Treasury publishes; we checked that our formula reproduces it on 652 auctions of 2023 and 2024.
Savings bond rates move on a different calendar, every May 1 and November 1: their history is on the I bond fixed rate history page. Both kinds of interest are free of state and local income tax, which the state tax page converts into a taxable-equivalent yield.