T-Bill vs Savings Account & HYSA Calculator
Compare Treasury Bills against High-Yield Savings Accounts (HYSA) after all taxes. T-Bills lock in a rate and skip state tax — HYSAs offer instant access but variable rates. Enter your details to see which wins after taxes.
Amount you plan to invest in either option.
Current T-Bill auction rate from TreasuryDirect.gov.
Savings account will be compared over the same period.
APY from your bank or HYSA (e.g. Marcus, Ally, SoFi).
Your marginal federal income tax bracket.
Enter your state's income tax rate. Examples: CA = 13.3%, NY = 10.9%, TX/FL = 0%. T-Bills are exempt from state tax — savings accounts are not. Find your rate →
T-Bill vs Savings Account — Full Comparison
| Feature | T-Bills | Savings / HYSA |
|---|---|---|
| Issuer | U.S. Government (Treasury) | FDIC-insured bank |
| Safety | U.S. Gov backed — no limit | FDIC insured up to $250,000 |
| Rate Type | Fixed at auction — locked in | Variable — can drop anytime |
| Federal Tax | ✅ Yes — ordinary income | ✅ Yes — ordinary income |
| State Tax | ✅ Exempt by federal law | ❌ Fully taxable |
| Liquidity | Fixed maturity — no early exit on TreasuryDirect | Withdraw anytime, no penalty |
| Min. Investment | $100 on TreasuryDirect | Often $0 — no minimum |
| Over $250K | ✅ No limit — fully government backed | ❌ Not insured above $250K per bank |
| Rate Stability | Locked in at purchase | Can be cut anytime by the bank |
T-Bill vs HYSA — The Key Difference
Both T-Bills and HYSAs are safe, competitive options for idle cash. The critical differences are rate stability and state tax treatment:
When Should You Choose T-Bills?
- You live in a high state-tax state (CA, NY, NJ, OR) — state tax exemption adds real value
- You won't need the money for at least 4 weeks — can commit to a fixed maturity
- You want to lock in today's rate before the Fed cuts — HYSA rates fall immediately after cuts
- You have more than $250,000 — T-Bills have no insurance cap unlike bank accounts
- You want the absolute safest investment — U.S. government vs FDIC-insured bank
When Should You Use a Savings Account or HYSA?
- You need instant access to your money anytime — emergency fund, daily expenses
- You live in a state with no income tax (TX, FL, NV) — the T-Bill tax advantage disappears
- You want zero setup — no TreasuryDirect account needed
- You want to start with less than $100
- Your HYSA rate is significantly above current T-Bill rates
Find your real after-tax T-Bill yield and the HYSA rate needed to match it.
Related Calculators
Learn more: What Are Treasury Bills — Complete Guide · Are T-Bills Worth It? · Best T-Bill Duration Guide
Frequently Asked Questions
Are T-Bills better than a high-yield savings account?
For money you won't need for 1–12 months, T-Bills often win after taxes — especially in high-tax states. T-Bills lock in a rate at purchase (savings account rates can drop anytime) and are exempt from state tax. The main downside is you cannot access the money until maturity, while savings accounts allow withdrawals anytime.
What is the key difference between T-Bills and savings accounts?
The biggest differences are rate stability and liquidity. A T-Bill rate is locked in the moment you buy — your bank can lower your savings rate tomorrow. But savings accounts let you withdraw anytime with no penalty, while T-Bills have a fixed maturity date. T-Bills also skip state tax; savings account interest is fully taxable.
Which is better for an emergency fund?
A high-yield savings account is better for your core emergency fund because you can access the money instantly without penalty. T-Bills work well for the portion of your emergency fund you know you won't need for at least 4 weeks. Many investors keep 1–2 months of expenses in a savings account and the rest in a T-Bill ladder for higher yield.
Can I lose money in T-Bills compared to a savings account?
No — if held to maturity, T-Bills guarantee your full face value back. Savings accounts are also safe up to FDIC limits ($250,000). The only scenario where you could get less than expected from a T-Bill is selling before maturity on the secondary market, where prices fluctuate slightly with interest rates.