Treasury Bill Calculator: T-Bill Price & Yield [Free]

4-week	$32.32
6-week	$48.47
8-week	$64.63
13-week	$105.03
17-week	$137.35
26-week	$210.06
52-week	$420.12

A Treasury bill calculator turns a T-bill's discount rate into what you pay, what you earn and its true yield. Price per $100 = 100 × (1 − rate × days ÷ 360). A $10,000 26-week bill at a 4.155% discount rate costs $9,789.94, pays $10,000 at maturity, earns $210.06 and has an investment rate of 4.303%.

The maths follows the U.S. Treasury's own rules in 31 CFR Part 356, Appendix B, and the calculator reproduces published TreasuryDirect auction results to the last decimal (see the check table below).

How to use this T-bill calculator

Enter the face value (par) you want back at maturity. TreasuryDirect sells bills from $100 in $100 steps.
Pick the term: 4, 6, 8, 13, 17, 26 or 52 weeks.
Enter the discount rate (the “high rate” in an auction result) or switch to price per $100 if you have that instead.
Leave days in year at 365 unless the year after the issue date includes February 29.
Read what you pay, the interest earned and the investment rate. The chart shows what the same rate would earn on every term.

How it's calculated

All formulas are from 31 CFR Part 356, Appendix B, Section VI, which TreasuryDirect links as its detailed formula reference.

Price per $100: P = 100 × (1 − d × r ÷ 360), where d is the discount rate in decimals and r is days to maturity. Prices are rounded to six decimals.
Your cost: face value ÷ 100 × P. Interest = face value − cost.
Discount rate from a price: d = ((100 − P) ÷ 100) × (360 ÷ r).
Investment rate, terms up to a half-year: i = ((100 − P) ÷ P) × (y ÷ r), where y is 365, or 366 if the year after issue contains February 29.
Investment rate, terms over a half-year: solve P[1 + (r − y/2)(i/y)](1 + i/2) = 100. Rewritten as a quadratic, i = (−b + √(b² − 4ac)) ÷ 2a with a = r/2y − 0.25, b = r/y and c = (P − 100)/P.

Days to maturity are weeks × 7 here. Real bills can run a day longer or shorter when a holiday moves the issue or maturity date, so check the auction announcement for exact days.

Check against real Treasury auctions

These are published TreasuryDirect results. The calculated columns come from the calculator's formulas.

Bill (issue date)	High rate	Published price / inv. rate	Calculated price / inv. rate
4-week (Sep 29, 2026, 28 days)	3.850%	99.700556 / 3.915%	99.700556 / 3.915%
26-week (Sep 24, 2026, 182 days)	4.155%	97.899417 / 4.303%	97.899417 / 4.303%
52-week (Sep 3, 2026, 364 days)	3.980%	95.975778 / 4.161%	95.975778 / 4.161%

Worked examples

$10,000 in a 26-week T-bill at 4.155%

r = 182 days. P = 100 × (1 − 0.04155 × 182 ÷ 360) = $97.899417. Cost = 100 × P = $9,789.94. Interest = $210.06. Because 182 days is not more than a half-year, the investment rate is ((100 − P) ÷ P) × (365 ÷ 182) = 4.303%.

$1,000 in a 4-week T-bill at 3.85%

P = $99.700556, so you pay $997.01 and get $1,000 back 28 days later: $2.99 of interest, an investment rate of 3.915%. Short bills earn small dollar amounts because you hold them for only a few weeks.

$5,000 in a 52-week T-bill at 3.98%

P = $95.975778; cost $4,798.79; interest $201.21. At 364 days this bill is longer than a half-year, so the quadratic formula applies and gives 4.161%. For comparison, a 52-week bill at the 26-week bill's 4.155% discount rate would yield 4.350% — the longer the bill, the bigger the gap between discount rate and yield.

From a price instead of a rate

An 8-week (56-day) bill priced at $99.379333 per $100 has a discount rate of 3.990%. A $10,000 bill costs $9,937.93 and earns $62.07, an investment rate of 4.071%.

T-bill price per $100 by discount rate

Discount rate	4-week	13-week	26-week	52-week
3.000%	99.766667	99.241667	98.483333	96.966667
3.500%	99.727778	99.115278	98.230556	96.461111
4.000%	99.688889	98.988889	97.977778	95.955556
4.500%	99.650000	98.862500	97.725000	95.450000
5.000%	99.611111	98.736111	97.472222	94.944444

Interest earned on a $10,000 Treasury bill

Interest at maturity, with the investment rate in brackets (365-day year).

Discount rate	4-week	13-week	26-week	52-week
3.000%	$23.33 (3.049%)	$75.83 (3.065%)	$151.67 (3.089%)	$303.33 (3.113%)
3.500%	$27.22 (3.558%)	$88.47 (3.580%)	$176.94 (3.613%)	$353.89 (3.646%)
4.000%	$31.11 (4.068%)	$101.11 (4.097%)	$202.22 (4.139%)	$404.44 (4.183%)
4.500%	$35.00 (4.579%)	$113.75 (4.615%)	$227.50 (4.669%)	$455.00 (4.724%)
5.000%	$38.89 (5.089%)	$126.39 (5.134%)	$252.78 (5.201%)	$505.56 (5.270%)

T-bill facts from TreasuryDirect

Terms: 4, 6, 8, 13, 17, 26, 52 weeks. The 4- to 26-week bills are auctioned weekly; the 52-week bill every four weeks.
Minimum: $100, in $100 increments. Maximum: $10 million per auction by non-competitive bid.
How interest works: bills are sold at a discount or at par, and you receive face value at maturity. The difference is your interest; there are no coupon payments.
Buying: in TreasuryDirect you bid non-competitively and accept the rate set at auction. Banks and brokers also sell bills.

Taxes on Treasury bill interest

IRS Publication 550 says interest on Treasury bills, notes and bonds is subject to federal income tax but exempt from all state and local income taxes. For a T-bill, the discount (face value minus what you paid) is the interest, and you generally report it in the year the bill matures. That state exemption is worth most to people in high-tax states when comparing a T-bill with a CD or high-yield savings account, whose interest is usually taxed by the state as well.

Common mistakes

Comparing the discount rate with a CD rate. The discount rate understates your return. Compare the investment rate instead.
Assuming the rate before the auction. Your rate is set at auction. Recent results are a guide, not a promise.
Forgetting reinvestment. A 4-week bill's yield applies for four weeks only. If you roll it over, the next bill may pay more or less.
Selling early. The figures here assume you hold to maturity. A sale before maturity is at the market price.

Treasury notes, bonds and I bonds

This calculator covers bills only. Other Treasury securities work differently, so a T-bill formula won't price them:

Treasury notes mature in 2, 3, 5, 7 or 10 years and pay a fixed interest rate every six months.
Treasury bonds mature in 20 or 30 years and also pay interest every six months. Both start at $100 in $100 steps.
I bonds are savings bonds with a rate that combines a fixed rate and an inflation rate reset every six months. You can cash one in after 12 months, but before 5 years you lose the last 3 months of interest. Check TreasuryDirect for the current rate.

Is a T-bill right for your cash?

Bills suit money you will need within a year: an emergency fund top-up, a tax bill or a planned purchase. They pay a fixed amount if held to maturity. For retirement savings, compare with the 401(k) calculator, or see how long savings last with the how long will my money last calculator. Federal employees can compare with the G Fund using the TSP calculator.

This page is general information, not financial or tax advice. Rates change at every auction; check the latest results on TreasuryDirect and talk to a tax professional about your own situation.

Frequently asked questions

How do you calculate the price of a Treasury bill?

Price per $100 = 100 × (1 − discount rate × days to maturity ÷ 360), rounded to six decimals (31 CFR 356, Appendix B). Multiply by face value ÷ 100 for your cost. A 26-week (182-day) bill at 4.155% costs $97.899417 per $100, so a $10,000 bill costs $9,789.94.

How much interest will I earn on a $10,000 T-bill?

At a 4.155% discount rate, a 26-week $10,000 bill costs $9,789.94 and pays $10,000 at maturity, so you earn $210.06. For a 52-week bill at 3.98% the same $10,000 would earn $402.42.

What is the difference between the discount rate and the investment rate?

The discount rate is based on face value and a 360-day year. The investment rate (coupon-equivalent or bond-equivalent yield) is based on the price you actually pay and a 365- or 366-day year, so it is always higher. Use the investment rate to compare a T-bill with a CD or savings account.

Why is the 52-week bill formula different?

For bills of not more than a half-year to maturity, Treasury uses i = ((100 − P) ÷ P) × (y ÷ r). For bills longer than a half-year it assumes a coupon bond would have paid a half-year coupon, and solves P[1 + (r − y/2)(i/y)](1 + i/2) = 100 with the quadratic formula. A 26-week bill (182 days) uses the first formula; a 52-week bill (364 days) uses the second.

Is T-bill interest taxable?

T-bill interest is subject to federal income tax but exempt from all state and local income taxes (IRS Publication 550; TreasuryDirect). You generally report the interest in the year the bill matures, and you should receive Form 1099-INT.

What is the minimum amount to buy a Treasury bill?

$100, in increments of $100, per TreasuryDirect. The maximum is $10 million per auction with a non-competitive bid, or 35% of the offering amount with a competitive bid.

What terms do Treasury bills come in?

TreasuryDirect sells bills in 4, 6, 8, 13, 17, 26 and 52-week terms. The 4- to 26-week bills are auctioned weekly and the 52-week bill every four weeks. Cash management bills with variable terms are sold only through banks, brokers and dealers.

What rate will I get if I buy on TreasuryDirect?

In a TreasuryDirect account you must bid non-competitively, which means you accept the rate set at the auction. That is the high rate on the auction results, and the price per $100 on the results is what you pay.

Can I sell a T-bill before it matures?

Yes. TreasuryDirect says you can hold a bill until it matures or sell it before then. If you sell early, the price depends on market rates at the time, so you could get more or less than this calculator's figure, which assumes you hold to maturity.

Is a 6-month T-bill the same as a 26-week T-bill?

Yes. The 26-week bill is usually 182 days, just under half a year, so its investment rate uses the simple formula. At a 4.155% discount rate its investment rate is 4.303%.

Sources & method

Results are estimates for general information. Found an error? It helps everyone — see our methodology.

Treasury Bill Calculator: T-Bill Price & Yield