As of Oct. 16, 2026
Short answer: Compare
after-tax dollars, not headline rates. Treasury's latest 13-week bill paid an investment rate of
4.185% (auction 2026-10-13); the best standard savings APY we track is
4.2% (EverBank, read 2026-10-12). T-bill interest is
free of state and local income tax; savings interest isn't, so the more state tax you pay, the better the bill looks. On $10,000 for 13 weeks with a 22% federal bracket (example): with a 5% state tax, the T-bill comes out about $6.12 ahead; with no state income tax, too close to call (savings would need about 4.25% APY to match). Savings stays available any day.
Savings is FDIC-insured; T-bills aren't, but they're backed by the full faith and credit of the U.S. government. Run your numbers.
Sources: Treasury auction data · TreasuryDirect: bills · 31 U.S.C. 3124 · FDIC · TreasuryDirect
Best move: emergency fund in savings, then compare after tax
Keep your emergency fund in an FDIC-insured savings account. For money you won't touch until a bill matures, compare after tax: the more state income tax you pay, the better the bill looks; with none, it comes down to the two rates that day.
The math:
- $10,000 into the latest 13-week bill at $98.967403 per $100 buys 101 bills ($10,100 face) for $9,995.71; interest at maturity in 91 days: $104.29.
- The same $9,995.71 in savings at 4.2% APY for 91 days earns $103.06.
- With a 22% federal bracket and a 5% state tax (examples): T-bill $81.35 vs savings $75.23 after tax. Savings would need about 4.55% APY to match.
- With no state income tax: T-bill $81.35 vs savings $80.38; break-even savings APY about 4.25%.
Sources: Treasury auction data · TreasuryDirect: bills · 31 U.S.C. 3124 · IRS Pub. 550 · TreasuryDirect: selling
A best fit for the situation described, not financial advice or a buy/sell recommendation. Partner links never change a pick.
Your roadmap
- Set aside your emergency fund first in an FDIC-insured savings account you can reach the same day.
- Look up your state income tax rate on interest. If it's zero, the T-bill's tax break is worth nothing to you.
- Run the calculator with your amount, brackets and the bill length that matches when you'll need the money.
- If you buy in TreasuryDirect, plan to hold to maturity. You must hold 45 days before selling, so a 4-week bill can't be sold early there.
- Keep your Form 1099-INT: T-bill interest goes on your federal return for the year the bill matures, and comes off your state return.
Latest Treasury bill auction results
| Bill | Auction | Matures | Price per $100 | Discount rate | Investment rate |
|---|
| 4-Week | 2026-10-15 | 2026-11-17 | $99.688889 | 4.000% | 4.068% |
| 6-Week | 2026-10-13 | 2026-11-27 | $99.524611 | 3.980% | 4.055% |
| 8-Week | 2026-10-15 | 2026-12-15 | $99.370000 | 4.050% | 4.132% |
| 13-Week | 2026-10-13 | 2027-01-14 | $98.967403 | 4.085% | 4.185% |
| 17-Week | 2026-10-14 | 2027-02-16 | $98.613319 | 4.195% | 4.313% |
| 26-Week | 2026-10-13 | 2027-04-15 | $97.876667 | 4.200% | 4.351% |
| 52-Week | 2026-09-29 | 2027-09-30 | $95.551111 | 4.400% | 4.616% |
High (accepted) price and rates from each term's most recent regular auction (cash management bills left out). Source: U.S. Treasury Fiscal Data, read 2026-10-16. All successful bidders, including non-competitive bids (the only kind TreasuryDirect accepts), get the rate of the highest accepted bid. TreasuryDirect: auctions The investment rate is the one to compare with other yields. We recomputed every investment and discount rate above from the price with Treasury's own formulas, and they match. 31 CFR 356 App. B
Why your T-bill math looks off
Treasury publishes two rates for each bill, and neither is an APY:
- Discount rate: the discount divided by the face value, on a 360-day year. It always looks lower. Formula: (100 − price) ÷ 100 × 360 ÷ days.
- Investment rate (coupon-equivalent yield): the discount divided by what you paid, on a 365-day year (366 if the year after issue has Feb. 29). Formula for bills of half a year or less: (100 − price) ÷ price × 365 ÷ days. 52-week bills use a longer formula from the same regulation.
Worked example from the 2026-10-15 4-week auction: price $99.688889 per $100, 28 days.
- Investment rate: (100 − 99.688889) ÷ 99.688889 × 365 ÷ 28 = 4.068% (Treasury published 4.068%).
- Discount rate: (100 − 99.688889) ÷ 100 × 360 ÷ 28 = 4.000% (published 4.000%).
- The common shortcut, (100 ÷ price − 1) × 52 ÷ 4, gives 4.057%. It's close; it's just using 52 weeks instead of 365 days. If your result is close to Treasury's investment rate, your math is fine.
- Neither rate compounds. If you could roll 4-week bills at that same price all year, it would work out to about 4.15% a year, but every new bill gets that week's price.
Sources: 31 CFR 356 App. B · TreasuryDirect: pricing
Savings vs T-bills vs Treasury bill funds
| Item | High-yield savings | T-bill | Treasury bill ETF or fund | Source |
|---|
| Who backs it | FDIC insurance up to $250,000 per depositor, per bank, per ownership category | Full faith and credit of the U.S. government; not FDIC-insured | Not FDIC-insured or government-guaranteed; the fund holds Treasuries | FDIC · TreasuryDirect · SEC Investor.gov: ETFs |
| Getting your money | Any day | At maturity (4 to 52 weeks). In TreasuryDirect, hold 45 days before you can sell through a bank or broker | Sell shares on any trading day at the market price | TreasuryDirect: bills · TreasuryDirect: selling · SEC Investor.gov: ETFs |
| Can the value drop? | No (balance stays; the rate can change) | Held to maturity you get face value; selling early is at the market price | Yes; the market price can be above or below the fund's net asset value | TreasuryDirect: bills · SEC Investor.gov: ETFs |
| Federal tax | Yes | Yes, for the year the bill matures (Form 1099-INT, box 3) | Yes (fund dividends) | IRS Pub. 550 |
| State and local income tax | Yes | No | Depends on your state; California exempts only the U.S.-obligation part, and only if at least 50% of the fund is U.S. obligations | 31 U.S.C. 3124 · California FTB |
| Minimum | Set by the bank | $100, in $100 steps | Varies by broker | TreasuryDirect: bills |
Treasury bill ETFs and funds
Questions like "HYSA or SGOV/VBIL?" are about Treasury ETFs. These rules apply to any of them; we don't rate individual funds on this page.
- Not FDIC-insured. The SEC says ETFs aren't guaranteed or insured by the FDIC or any other government agency, and you can lose money. SEC Investor.gov: ETFs
- Price can move. ETF shares trade at market prices that can be above or below the fund's net asset value, so you may get more or less than NAV when you sell, and the fund's dividends can change as rates change. SEC Investor.gov: ETFs
- The state tax break isn't automatic. California, for example, exempts fund dividends from U.S. obligations only if at least 50% of the fund's assets qualify, and only the share the fund reports on your annual statement or 1099-DIV statement. Check your own state's rule. California FTB
- Funds charge ongoing expenses (the expense ratio), which come out of what they pay you. Check the fund's prospectus.
Show me the details
How to buy a T-bill
- TreasuryDirect (treasurydirect.gov): bids there are non-competitive: $100 minimum, in $100 steps, up to $10 million per auction, at the auction's rate. Treasury holds the bill for you. TreasuryDirect: bills · TreasuryDirect: auctions
- A bank or broker: you can buy at auction or on the market, and sell before maturity. TreasuryDirect says selling through a bank or broker normally costs a fee. TreasuryDirect FAQ
- Selling early from TreasuryDirect: you have to hold the bill 45 days, then transfer it to a bank or broker to sell. A 4-week bill matures before that, so it can't be sold or transferred from TreasuryDirect. TreasuryDirect: selling
Taxes
- Interest from Treasury bills is subject to federal income tax and exempt from all state and local income taxes. IRS Pub. 550 · 31 U.S.C. 3124
- You generally report it when the bill is paid at maturity, so a bill bought in December that matures in January counts for the next tax year. You'll get Form 1099-INT with the interest in box 3. IRS Pub. 550
How the calculator works
- It buys as many $100-face bills as your amount covers at the bill's price, and puts the same dollars in savings for the same number of days.
- T-bill interest = face value − price paid. Savings interest = amount × ((1 + APY) ^ (days ÷ 365) − 1).
- After tax: the bill loses only federal tax; savings loses federal plus state and local tax. The break-even APY is the savings rate that would give the same after-tax dollars.
- Results within 0.10 percentage points of APY are called too close to call.
Limits of this page
- Not investment advice. Facts and arithmetic only; we don't recommend a fund, broker or bank here.
- Savings rates can change at any time, and every new bill gets its own auction price. The calculator holds both steady for one bill's term.
- It doesn't model deducting state tax on your federal return, the alternative minimum tax, or selling a bill early.
- The 22% and 5% tax rates are examples, not your rates.
Why trust this: bill rates come straight from Treasury's auction results, dated, and we recompute them with Treasury's own formulas. The savings rate is the best standard APY we track from bank pages, dated. Example tax rates are labeled.
Not investment advice. We republish Treasury, IRS, FDIC and SEC facts with dates and do simple math on what you type. Rates change; check the current auction and your bank before you move money.
Sources & as-of dates
- U.S. Treasury Fiscal Data: Treasury Securities Auctions Data (bill auction results) (updated after each auction; checked 2026-10-16)
- TreasuryDirect: Treasury Bills (terms, $100 minimum, taxes) (read Oct. 16, 2026; checked 2026-10-16)
- TreasuryDirect: Understanding Pricing and Interest Rates (read Oct. 16, 2026; checked 2026-10-16)
- 31 CFR Part 356, Appendix B: formulas for bill discount rates and investment rates (eCFR current as of Oct. 15, 2026; checked 2026-10-16)
- TreasuryDirect: How Auctions Work (everyone gets the high accepted rate; non-competitive bids) (read Oct. 16, 2026; checked 2026-10-16)
- TreasuryDirect: About Treasury Marketable Securities (full faith and credit) (read Oct. 16, 2026; checked 2026-10-16)
- TreasuryDirect: Selling a Treasury Marketable Security (45-day hold) (read Oct. 16, 2026; checked 2026-10-16)
- TreasuryDirect: FAQs about Treasury Marketable Securities (selling through a broker normally costs a fee) (read Oct. 16, 2026; checked 2026-10-16)
- 31 U.S.C. § 3124: U.S. obligations exempt from state and local taxation (current U.S. Code; checked 2026-10-16)
- IRS Publication 550 (2025): Investment Income and Expenses, U.S. Treasury bills (2025 edition, read Oct. 16, 2026; checked 2026-10-16)
- FDIC: Understanding Deposit Insurance (what is and isn't covered) (read Oct. 16, 2026; checked 2026-10-16)
- SEC Investor.gov: Exchange-Traded Funds (ETFs) (read Oct. 16, 2026; checked 2026-10-16)
- California FTB: 2025 Instructions for Schedule CA (540), line 2 (exempt-interest dividends, 50% rule) (2025 tax year, read Oct. 16, 2026; checked 2026-10-16)
Estimates, not financial advice. Taxes, insurance, PMI and fees vary by lender, county and city; confirm with your lender, dealer and state agency before acting.