T-Bill vs CD Calculator
Work out a Treasury bill’s price, interest and yield from its rate, and compare what you keep with a CD after federal and state tax.
T-bill interest
$103.40
buy $10,100 of face value for $9,996.60 · yield 4.15%
CD interest
$105.52
on $10,000 at 4.30% APY for 91 days
After tax, the T-bill is ahead by
$3.62
a CD would need about 4.51% APY to match the T-bill
Interest you keep
The numbers in detail
| T-bill | CD | |
|---|---|---|
| Price per $100 of face value | $98.9763 | — |
| Amount invested | $9,996.60 ($3.40 left over) | $10,000.00 |
| Paid back at maturity | $10,100.00 | $10,105.52 |
| Interest | $103.40 | $105.52 |
| Yield | 4.15% investment rate | 4.30% APY |
| Federal tax | $22.75 | $23.21 |
| State and local tax | $0.00 (exempt) | $5.28 |
| Interest you keep | $80.65 | $77.03 |
How a Treasury bill pays you
A Treasury bill is a short loan to the US government, for four weeks to one year. It pays no interest along the way. Instead you buy it for less than its face value and receive the full face value at maturity; the difference is your interest. At auction the price is set by the discount rate, so a 13-week bill at 4.05% sells for about $98.98 per $100 of face value. Because you pay less than $100, your actual return, the investment rate or yield, is a little higher than the discount rate. Bills are sold in multiples of $100, so a small part of your money may be left over.
Why tax changes the comparison
Interest on Treasury bills is taxed by the federal government but not by states or cities. CD interest is taxed by both. In a state with income tax, a T-bill can therefore leave you with more money than a CD that advertises a higher rate. The calculator shows the CD rate you would need to match the T-bill after tax. Our guide to T-bills, CDs and money market funds compares the options in more detail.
What the calculator assumes
The bill is bought at the price implied by the rate you enter and held to maturity. Bills of more than six months use the Treasury’s formula for longer bills. The CD earns the APY you enter for the same number of days, with interest compounding. Tax is applied at the flat rates you choose, without deductions or credits, and early withdrawal from the CD is not allowed for. Default discount rates are the latest auction results in early October 2026; rates change every week, so use the rate your broker, TreasuryDirect or bank quotes today.
An estimate for planning, not a quote. Treasury bills are backed by the US government; CDs at insured banks are covered by the FDIC up to $250,000 per depositor, per bank, per ownership category. Tax treatment is simplified. Not tax or investment advice.