T-bill calculator: price, yield and interest

A Treasury bill is sold at a discount and pays its face value at maturity, so the interest is the gap between the two. The calculator prices any bill from its auction rate and sets the result beside an onchain yield over the same term.

A T-bill calculator turns a bill's discount rate into three numbers: what the bill costs today, how much interest it pays at maturity and the yield that interest works out to over a year. The US Treasury sells bills in terms of 4, 6, 8, 13, 17, 26 and 52 weeks, and it pays no coupon on any of them. The buyer pays less than face value and receives the full face value when the bill matures, and TreasuryDirect treats that difference as the interest. The calculator below loads the most recent auction rate for each term straight from the Treasury's public data and lets you change any input.

Bills matter well beyond the brokerage account. They sit behind most of the dollar stablecoins in circulation and inside the tokenized money market funds that onchain treasuries hold, so the T-bill rate is the floor that most onchain dollar yield is measured against. The second half of the calculator compares a bill with any onchain APY over the same number of days, after state tax.

T-bill calculator

Enter the face value you want at maturity and pick a term. The discount rate fills in from the latest auction for that term, and you can overwrite it to price a bill bought in the secondary market or at an older auction.

How do you calculate the interest on a T-bill?

T-bill interest equals the face value minus the price paid, and the price comes from the discount rate set at auction. The Treasury's pricing formula is Price = Face value × (1 − discount rate × days / 360). The formula uses a 360-day year, a money-market convention that makes the discount rate a little lower than the return you actually earn. For a 26-week bill at the 21 September 2026 auction, the high discount rate was 4.155% over 182 days, which gives a price of $97.899417 per $100 of face value.

Holding that bill to maturity turns $9,789.94 into $10,000, so a $10,000 bill earns $210.06 of interest. The bill makes no interest payments before maturity. A holder who needs the money early sells it through a broker, and because a bill's price climbs toward face value as maturity approaches, the sale price captures most of the return earned so far, though it rises or falls with any change in rates since the purchase. The same arithmetic works for any term, which is why the calculator only needs the face value, the number of days and the rate.

Discount rate vs investment rate

The discount rate and the investment rate describe the same bill in two ways, and the investment rate is the one to compare with other yields. The discount rate measures the discount against face value on a 360-day year. The investment rate, also known as the bond-equivalent yield, measures the interest against the price you actually paid on a 365-day year, and it's always the higher of the two.

The rates in the table come from the Treasury's auction results on Fiscal Data, and the calculator reproduces every investment rate in it to three decimal places. Bills of 26 weeks or less use a simple formula. The 52-week bill uses a longer one that assumes semiannual compounding, so its investment rate lines up with the yield on Treasury notes.

How much does a $10,000 T-bill pay?

At the September 2026 auction rates, a $10,000 bill pays about $30 of interest over 4 weeks, $101 over 13 weeks, $210 over 26 weeks and $402 over 52 weeks. Those figures come straight from the pricing formula above, and the calculator gives the exact figure for any term and amount. Rolling a short bill into a new one at each maturity compounds the return, which is why the calculator also shows each rate as an APY. If rates fall between auctions, the rolled return falls with them, so the APY figure holds only while the rate stays where it is.

Are T-bills tax free?

T-bill interest is subject to federal income tax and exempt from state and local income tax, according to TreasuryDirect. The exemption matters most to buyers in high-tax states, because a taxable alternative has to pay more to leave the same amount after state tax. The calculator's break-even box shows that rate: at a 4.35% bill APY and a 9% state tax rate, a state-taxed alternative needs to pay about 4.78% to match.

Onchain yield is generally taxable at both the federal and state level, though the treatment depends on the product and on where the holder lives. The calculator assumes the onchain yield is taxed by the state and that both are taxed federally. It's a simplification to show how the exemption changes the comparison, and it's general information only, not tax advice.

How to buy T-bills

Individuals and entities can buy bills directly from the Treasury through a TreasuryDirect account, or through a bank or broker. TreasuryDirect accepts non-competitive bids only, which means the buyer accepts whatever rate the auction sets, with a minimum of $100 in $100 increments and a maximum of $10 million per auction, as its buying guide sets out. Bills bought there must be held for at least 45 days before they can be moved to a broker and sold. A brokerage account can also buy bills in the secondary market and sell them before maturity, which is the usual route for anyone who might need the money early.

T-bills vs onchain yield

Onchain dollar yield starts from the same place as the bill rate. Fiat-backed stablecoins hold much of their reserves in short-dated bills, and under the GENIUS Act issuers can't pass that interest to holders for simply holding the coin. Tokenized Treasury funds pass it through as a share price that rises with the bill yield, less a management fee, and many are open only to qualified or non-US buyers. RWA-backed stablecoins and curated vaults sit a step further out and add lending, liquidity or credit returns on top.

Comparing the two fairly takes a like-for-like rate, which is the APY for both. A vault's share price captures the strategy's return after fees, so the APY built from it is the number to enter in the calculator. Upshift runs curated stablecoin vaults whose trailing APY comes from that share price, and our explainer on APY in crypto covers how that APY is calculated. An onchain yield above the bill rate pays for extra risk, and the vault guide sets out what to check before depositing. Always make sure to do your own research and be aware of the above and any other risks before depositing.

Frequently asked questions

What is the formula for a T-bill price?

Price = Face value × (1 − discount rate × days to maturity / 360). A 26-week bill at a 4.155% discount rate prices at $97.899417 per $100 of face value.

Is the T-bill rate the same as the yield?

The quoted discount rate understates the yield slightly because it's measured against face value on a 360-day year. The investment rate is the yield to compare with savings accounts, money market funds and onchain APYs.

How often are T-bills auctioned?

The 4, 6, 8, 13, 17 and 26-week bills are auctioned every week, and the 52-week bill every four weeks, according to TreasuryDirect.

Can you lose money on a T-bill?

A bill held to maturity pays its full face value. A bill sold before maturity can fetch less than the buyer paid if rates have risen in the meantime.

Do T-bills pay monthly interest?

Bills pay no interest along the way. The full return arrives at maturity as the difference between the price paid and face value.

Why do stablecoins hold T-bills?

Bills are short-dated, liquid and backed by the US government, which makes them a common reserve asset for fiat-backed stablecoins. The interest they earn goes to the issuer, and our post on how stablecoins make money traces where it goes.

Keep reading

• Tokenized treasuries compared. Funds by size, eligibility and exit speed.
• Where USDC yield comes from. Current USDC rates by venue.
• What is an onchain vault? A guide for treasury teams.