6-Month T-Bill Calculator
Calculate the exact purchase price, earnings, and annualized yield for a 6-month (26-week, 182-day) Treasury Bill — the most popular T-Bill duration. Just enter your face value and current discount rate.
Minimum $100 — T-Bills are sold in $100 increments on TreasuryDirect.
Use the latest 26-week T-Bill auction rate from TreasuryDirect.gov.
Fixed at 182 days (26 weeks / 6 months) — auctioned every Monday.
What is a 6-Month T-Bill?
A 6-month Treasury Bill (also called a 26-week T-Bill) is the most widely purchased T-Bill duration by individual investors. It matures in 182 days and is auctioned every Monday by the U.S. Treasury. You buy it at a discount and receive the full face value at maturity — the difference is your earnings, guaranteed by the U.S. government.
6-Month T-Bill Formula
- Discount = Face Value × (Discount Rate / 100) × (182 / 360)
- Purchase Price = Face Value − Discount
- Annualized Yield = (Discount / Purchase Price) × (365 / 182) × 100
Face Value: $10,000 | Duration: 182 days
Discount = $10,000 × 4.5% × (182/360) = $227.50
Purchase Price = $10,000 − $227.50 = $9,772.50
Annualized Yield = ($227.50 / $9,772.50) × (365/182) × 100 = ~4.68%
Why is the 6-Month T-Bill the Most Popular?
The 26-week T-Bill hits the sweet spot between yield and flexibility. It earns more than shorter T-Bills while only locking your money up for 6 months — making it the go-to choice for investors who want a competitive return without committing a full year.
- Higher yield than 4-week and 13-week T-Bills in normal rate conditions
- Only a 6-month commitment — reassess every half year
- Auctioned weekly — easy to buy at any time
- Simple to auto-reinvest on TreasuryDirect for a hands-off approach
6-Month T-Bill vs Other Durations
| Duration | Days | Earnings on $10K at 4.5% | Annualized Yield | Best For |
|---|---|---|---|---|
| 4-Week | 28 | ~$35.00 | ~4.58% | Max flexibility |
| 13-Week | 91 | ~$113.75 | ~4.63% | Quarterly planning |
| 26-Week | 182 | ~$227.50 | ~4.68% | ⭐ Most popular — best balance |
| 52-Week | 364 | ~$455.00 | ~4.71% | Lock in rate for a year |
Need help choosing? Read our Best T-Bill Duration Guide for a full breakdown including how the rate environment affects your choice.
Tax Treatment of 6-Month T-Bills
Earnings from 6-month T-Bills are subject to federal income tax but are exempt from state and local taxes by federal law. In high state-tax states like California (13.3%), this exemption makes a 6-month T-Bill at 4.5% significantly more valuable than a CD at the same rate.
Find your real after-tax yield and the CD rate needed to match your T-Bill.
Rolling Over Your 6-Month T-Bill
When your 6-month T-Bill matures, you can reinvest the full face value into a new one. Rolling over twice gives you a full year of T-Bill returns. On TreasuryDirect, you can enable auto-reinvestment so the rollover happens automatically.
See how much you earn rolling over your 6-month T-Bill for 1–5 years.
Related Calculators
New to T-Bills? What Are Treasury Bills — Complete Guide · Are T-Bills Worth It? · Best T-Bill Duration Guide
Frequently Asked Questions
Is a 6-month T-Bill a safe investment?
Yes — 6-month T-Bills are backed by the U.S. government and carry no credit risk. If held to maturity (182 days), you are guaranteed to receive the full face value. They are widely considered one of the safest investments available.
How much can I earn from a 6-month T-Bill?
At a 4.5% discount rate, a $10,000 6-month T-Bill earns approximately $227.50 over 182 days, with an annualized yield of about 4.68%. At 5%, you would earn approximately $252.78 with a yield of about 5.20%.
Why is the 6-month T-Bill the most popular?
The 26-week T-Bill balances yield and flexibility better than any other duration. It earns more than shorter T-Bills while locking your money up for only 6 months — making it the most widely purchased T-Bill duration by individual investors.
Can I sell a 6-month T-Bill before maturity?
If purchased through TreasuryDirect, you cannot sell before maturity. If purchased through a brokerage like Fidelity or Schwab, you can sell on the secondary market at any time at the prevailing market price, which may be slightly above or below your purchase price.