13-Week T-Bill Calculator
The 13-week T-Bill matures in 91 days and is one of the best starting points for first-time investors. Enter your investment amount and current rate to see exactly what you pay, earn, and your annual return.
💡 A 13-week T-Bill is ideal for beginners — it offers a strong yield while letting you reassess your strategy every 3 months.
This is the amount you get back at maturity. Minimum $100.
Check latest rate → TreasuryDirect.gov
Fixed at 91 days (13 weeks) — auctioned every Monday.
How to Calculate 13-Week T-Bill Returns
- Enter your investment amount (face value)
- Apply the discount rate over 91 days
- Calculate the purchase price (face value minus discount)
- Convert your return into an annualized yield
This calculator performs all these steps instantly and shows your exact return.
What is a 13-Week T-Bill?
A 13-week Treasury Bill is a short-term U.S. government security that matures in 91 days (approximately 3 months). It is auctioned every Monday by the U.S. Treasury and is one of the most popular T-Bill durations for individual investors — offering a balance of competitive yield and quarterly liquidity.
Like all T-Bills, you buy it at a discount to face value and receive the full face value at maturity. The difference is your earnings — guaranteed by the U.S. government.
How 13-Week T-Bill Returns Are Calculated (Step-by-Step)
The formula (the calculator does this for you):
- Your profit = Investment × Rate ÷ 100 × 91 ÷ 360
- You pay upfront = Investment − Your profit
- Annual return = (Profit ÷ You pay) × (365 ÷ 91) × 100
Step 1 — Your profit:
$10,000 × 4.5% × (91 ÷ 360) = $113.75
Step 2 — What you pay today:
$10,000 − $113.75 = $9,886.25
Step 3 — Your annual return:
($113.75 ÷ $9,886.25) × (365 ÷ 91) × 100 = 4.62%
The return is slightly above 4.5% because it is calculated on what you actually paid ($9,886.25), not the full $10,000. In 3 months, you pocket $113.75 — then roll into a new 13-week bill or choose a longer duration.
Who Should Use the 13-Week T-Bill?
The 13-week T-Bill is widely considered the best starting point for first-time T-Bill investors. It is short enough to feel comfortable, matures quarterly for easy planning, and offers a competitive yield close to longer-duration T-Bills.
- First-time T-Bill investors wanting a short first commitment
- Investors who review their cash position quarterly
- People in rising rate environments — reinvest at higher rates every 3 months
- Aligning with quarterly estimated tax payments or financial planning
13-Week vs Other T-Bill Durations
| Duration | Days | Yield (typical) | Liquidity | Best For |
|---|---|---|---|---|
| 4-Week | 28 | Moderate | ⭐⭐⭐⭐⭐ | Max flexibility |
| 13-Week | 91 | Moderate-High | ⭐⭐⭐⭐ | Beginners, quarterly planning |
| 26-Week | 182 | High | ⭐⭐⭐ | Best balance — most popular |
| 52-Week | 364 | Highest (normal) | ⭐⭐ | Lock in rate for a year |
Not sure which duration fits your situation? Read our Best T-Bill Duration Guide for a full breakdown including how the rate environment affects your choice.
Tax Treatment of 13-Week T-Bills
Earnings from 13-week T-Bills are subject to federal income tax but are exempt from state and local taxes by federal law. This tax advantage makes T-Bills more attractive than CDs or savings accounts for investors in high state-tax states like California, New York, Oregon, or New Jersey.
Find your real after-tax yield and the CD rate needed to match your T-Bill.
Rolling Over Your 13-Week T-Bill
When your 13-week T-Bill matures, you can reinvest the full face value into a new one — this is called rolling over. On TreasuryDirect, you can enable auto-reinvestment so the rollover happens automatically with no action required.
Rolling over four times gives you a full year of T-Bill returns with quarterly compounding. Use our reinvestment calculator to see exactly how much you earn across multiple rollovers.
See how much you earn rolling over your 13-week T-Bill quarterly 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 (FAQ)
Is a 13-week T-Bill safe?
Yes, a 13-week T-Bill is a very safe investment backed by the U.S. government. If held to maturity, it guarantees full repayment with no credit risk.
How much does a 13-week T-Bill pay?
A 13-week T-Bill pays around $100 to $120 on a $10,000 investment depending on the rate. The exact earnings depend on the current discount rate and are paid at maturity.
Who should invest in 13-week T-Bills?
13-week T-Bills are ideal for beginners and investors who want quarterly liquidity. They provide a balance between yield and flexibility.
How often are 13-week T-Bills auctioned?
13-week T-Bills are auctioned weekly by the U.S. Treasury. This allows investors to enter the market regularly.