I Bond vs TIPS vs Treasury 2026 Inflation Protection Comparison

I bond vs TIPS comparison shows how three inflation-sensitive Treasury products would perform on the same investment amount, holding period, and inflation assumption. I bonds combine a fixed rate with a CPI-U variable rate. TIPS (Treasury Inflation-Protected Securities) adjust principal with CPI-U and pay a fixed real coupon. Treasury bills pay a nominal rate set at auction. Last updated May 2026.

How I Bonds Work in 2026

I bonds (Series I savings bonds) have two components: a fixed rate set for the life of the bond (currently ~1.20% based on recent issues), and a variable rate tied to non-seasonally adjusted CPI-U, reset every May and November. Composite rate = fixed + (2 × semiannual inflation) + (fixed × semiannual inflation). Purchase limit is $10,000/year per person electronic through TreasuryDirect, plus $5,000 in paper bonds via tax refund. Minimum 1-year hold; 3-month interest penalty if redeemed before 5 years. Tax-deferred until redemption; state-tax exempt.

How TIPS Work in 2026

TIPS are marketable Treasuries sold at auction in 5, 10, and 30-year terms. The principal adjusts daily with CPI-U; the coupon (real yield set at auction, currently ~2.10% for 10-year) is paid semiannually on the adjusted principal. No purchase limit. Liquid on the secondary market. Major drawback in taxable accounts: phantom income — both the coupon and the annual principal inflation adjustment are taxed each year as federal income, even though you don't receive the principal adjustment until maturity or sale. State-tax exempt.

How Treasury Bills Compare

T-bills are short-term (4, 13, 26, 52-week) zero-coupon Treasuries sold at a discount. The yield is a pure nominal rate — no inflation adjustment. T-bills win in low or negative inflation environments, when the Fed has hiked aggressively (current ~4.30%). They lose in high-inflation periods. State-tax exempt. Best for short-horizon cash management or as a "no inflation risk" benchmark.

Which Wins in Each Scenario

High inflation (4%+): I bonds and TIPS both crush T-bills. I bonds beat TIPS in small taxable accounts due to tax deferral and state exemption. TIPS beat I bonds in IRAs/401(k)s and for amounts above the $10K purchase cap. Moderate inflation (2-3%): TIPS and T-bills typically tie; I bonds with a 1.20%+ fixed rate beat both after tax. Low inflation (under 2%): T-bills win on nominal yield. Tax-advantaged account: TIPS shine — no phantom-income problem. Use the tool above to test your specific inflation assumption.

Sources: TreasuryDirect, IRS Pub 550. Rates change daily — verify before purchase.