T-Bill Ladder Calculator: Rolling Treasury Bill Ladder
This T-bill ladder calculator splits your cash into rungs of 4- to 52-week Treasury bills and turns the auction discount rate into price, interest, investment yield and after-tax income.
| Bill term | — |
| Number of rungs | — |
| Discount rate | — |
| Price per $100 of face value | — |
| Investment rate (coupon-equivalent yield) | — |
| Face value per rung | — |
| Cost per rung | — |
| Interest per rung at maturity | — |
| Total invested | — |
| Cash left over | — |
| Per year, if every rung rolls over at this rate | |
| Interest per year | — |
| Federal tax on interest | — |
| State and local income tax | — |
| After-tax interest per year | — |
| After-tax yield | — |
| Taxable-equivalent yield | — |
| State tax avoided per year | — |
A T-bill ladder is a set of Treasury bills bought at regular intervals so that one bill matures every week or every few weeks. Each maturing bill pays its face value, which you can spend or reinvest in a new bill. This calculator works out the rungs, the cost and interest of each rung, and your after-tax yield.
How a T-Bill Ladder Works
Example: split $52,000 across 13 weekly purchases of 13-week T-bills, $4,000 at each auction. After 13 weeks one bill matures every week. Reinvest each one in a new 13-week bill and the ladder keeps rolling: about $4,000 comes due every week while the rest earns the 13-week rate. The number of rungs follows from how often the Treasury auctions each term.
| Bill term | Auctioned | Usual auction day | Rungs in a full ladder |
|---|---|---|---|
| 4-week | Weekly | Thursday | 4 |
| 6-week | Weekly | Tuesday | 6 |
| 8-week | Weekly | Thursday | 8 |
| 13-week | Weekly | Monday | 13 |
| 17-week | Weekly | Wednesday | 17 |
| 26-week | Weekly | Monday | 26 |
| 52-week | Every four weeks | Tuesday | 13 (one matures every four weeks) |
Terms, frequency and the $100 minimum purchase (in $100 increments) are from TreasuryDirect; auction days are from its general auction timing page and can shift around holidays.
T-Bill Ladder Calculator Formulas: Discount Rate to Price and Yield
T-bills pay no coupon. You buy below face value and receive face value at maturity, and the difference is your interest. The calculator uses the Treasury’s own pricing formula and its coupon-equivalent yield formula:
Price per $100 = 100 × (1 − Discount Rate × Days ÷ 360)
Interest = Face Value − Price
Investment Rate = ((100 − Price) ÷ Price) × (365 ÷ Days)
The investment rate is always higher than the discount rate, because it measures interest against the price you paid over a 365-day year. For 52-week bills the Treasury uses a longer formula that allows for semiannual compounding, and so does this calculator. The Treasury also swaps 365 for 366 when the 12 months after the issue date include February 29; the calculator always uses 365, so in those periods the official investment rate is about 0.01 of a point higher. Press Load Example to run the 13-week auction of October 5, 2026 on $100,000:
| Step | Calculation | Result |
|---|---|---|
| Price per $100 | 100 × (1 − 0.0405 × 91 ÷ 360) | $98.976250 |
| Investment rate | (1.02375 ÷ 98.97625) × (365 ÷ 91) | 4.149% |
| Face value per rung | $100,000 ÷ 13 rungs, rounded down to a $100 multiple at that price | $7,700 |
| Cost and interest per rung | $7,700 × 0.9897625 | $7,621.17 and $78.83 |
| Interest per year | $78.83 × 13 rungs × 365 ÷ 91 | $4,110.36 |
| After 24% federal tax | $4,110.36 − $986.49 | $3,123.87 (3.15% of $99,075.23 invested) |
The 4.050% discount rate, $98.976250 price and 4.149% investment rate match the published result of that auction. Rates change at every auction, so check recent auction results before you rely on a yearly figure.
T-Bill Taxes: Federal Yes, State and Local No
The IRS says interest on Treasury bills, notes and bonds is subject to federal income tax but is exempt from all state and local income taxes. To compare a T-bill with a bank CD or savings account, whose interest is taxed at both levels, the calculator shows a taxable-equivalent yield:
Taxable-Equivalent Yield = T-Bill Yield × (1 − Federal Rate) ÷ (1 − Federal Rate − State Rate)
With a 4.149% investment rate, a 24% federal rate and a 6% state rate, that is 4.149% × 0.76 ÷ 0.70 = 4.50%. A fully taxable account would need to pay 4.50% to leave you the same after-tax income. The formula assumes you do not deduct state income tax on your federal return. In a state with no income tax the two yields are equal.
Where to Buy T-Bills
You can buy bills straight from the Treasury in a TreasuryDirect account, where the minimum is $100, or through a bank or broker. TreasuryDirect also lets you reinvest a maturing bill in a new one of the same type, which keeps a ladder rolling. Fees and order minimums at banks and brokers vary, so check before you buy. For a ladder of longer Treasuries see the Treasury bond ladder calculator, or compare with a CD ladder.
Last updated: October 2026. Sources: TreasuryDirect (terms, minimum, auction frequency, pricing formula), Treasury auction results for October 5, 2026, and IRS Topic 403.
Frequently Asked Questions
What is a T-bill ladder?
A T-bill ladder is a set of Treasury bills with staggered maturities — for example, 13 separate 13-week T-bills bought one week apart. One bill matures every week, giving you regular access to cash while the rest of the money earns the short-term Treasury rate.
Are T-bills state-tax-free?
Yes. The IRS states that interest on Treasury bills, notes and bonds is subject to federal income tax but is exempt from all state and local income taxes. The higher your state income tax rate, the more that exemption is worth. The calculator shows the taxable-equivalent yield for your own rates.
What yield do T-bills earn?
A T-bill is sold below face value and pays face value at maturity, and the difference is your interest. Auction results quote a discount rate and a higher investment rate, also called the coupon-equivalent yield, which is the return on the price you actually paid. At the October 5, 2026 auction the 13-week bill had a 4.050% discount rate and a 4.149% investment rate. Rates change at every auction.
Where do I buy T-bills?
Directly from the US Treasury through a TreasuryDirect account, or through a bank or broker. The Treasury sells bills from $100, in $100 increments. Banks and brokers can set their own fees and order minimums, so check before you place an order.
Are T-bills FDIC-insured?
No. FDIC insurance covers bank deposits, not securities. T-bills are direct obligations of the US Treasury, backed by the full faith and credit of the US government.
Is this calculator free?
Yes. Free, private, no sign-up. All math runs in your browser.
How do you build a T-bill ladder?
Pick a bill term, divide your money into one rung per auction, and buy one rung at each auction. With 13-week bills that is 13 rungs bought over 13 weeks. After that one bill matures every week. Reinvest each maturing bill in a new 13-week bill to keep the ladder rolling, or keep the cash when you need it.
How is T-bill interest calculated?
Price per $100 = 100 x (1 - discount rate x days to maturity / 360), and interest is face value minus price. For a 13-week (91-day) bill at a 4.050% discount rate the price is $98.976250 per $100, so a $1,000 bill costs $989.76 and pays $10.24 of interest at maturity.