I Bonds vs TIPS: Which Inflation Hedge Actually Wins?

The 60-second rule

If you’re investing $10,000 or less and can hold 5+ years, buy I Bonds — the 0.90% fixed rate plus tax deferral is the best risk-free deal available. At the worked example, I Bonds finish $206 ahead after taxes, and over 30 years the deferral gap grows to $3,645. If you need more than $10,000 of inflation protection, buy TIPS — they have no cap. And if the TIPS real yield is meaningfully above the I Bond’s fixed rate (about 0.97% at the defaults), TIPS win outright: at a 1.8% real yield, TIPS finish $376 ahead. The rule of thumb: the higher real rate wins; tax deferral narrows the gap.

How I Bonds work (the 4.26% number)

A Series I savings bond combines two rates. The fixed rate (0.90% for bonds bought May–October 2026) is set at purchase and never changes — it is your guaranteed real return for the bond’s 30-year life. The inflation rate (3.34% annualized right now, from CPI-U’s 1.67% six-month move) resets every six months for every I Bond ever issued. Together they make the 4.26% composite rate — up from 4.03% last cycle, announced by TreasuryDirect on May 1, 2026, resetting again November 1. Interest accrues monthly, compounds semiannually, and the composite can never go below 0% — your principal cannot fall. The catches: $10,000 a year per person through TreasuryDirect (plus $5,000 in paper bonds via your tax refund on Form 8888), no cashing out for 12 months, and a 3-month interest penalty if you redeem before 5 years. Taxes are federal only — no state or local — and you can defer the tax until you cash out, up to 30 years.

How TIPS work (the real-yield number)

Treasury Inflation-Protected Securities adjust your principal with CPI: inflation rises, your principal rises, and the fixed coupon pays on the bigger principal. You buy them at Treasury auction or on the secondary market, quoted in real yields — the return above inflation, locked at purchase if held to maturity. Two catches the brochure undersells. First, price risk: sell before maturity and you get the market price, which can be below what you paid — TIPS can lose money; I Bonds cannot. Second, phantom-income tax: the IRS taxes the inflation adjustment to your principal every year, even though you don’t receive that money until maturity — you pay tax on income you haven’t seen. Like I Bonds, TIPS are federal-tax only. The advantages: no purchase limit, maturities from 5 to 30 years, and — the big one — they can live inside an IRA, where the phantom-income problem disappears. I Bonds cannot be bought in an IRA at all.

The worked example, line by line

Defaults: $10,000, 5 years, 2.5% inflation, I-bond fixed 0.90%, TIPS real yield 0.50%, 22% bracket:

• I Bonds: semiannual composite = (1 + 0.90%/2) × (1 + 2.5%/2) − 1 = 1.7056% per half-year → 3.44% effective a year. $10,000 → $11,842 in 5 years (no penalty — redeemed at exactly 5). Tax deferred, then $1,842 of gain × 22% = $405 → $11,437 after tax.
• TIPS: nominal = (1 + 0.50%) × (1 + 2.5%) − 1 = 3.01% a year, but taxed every year: 3.01% × 78% = 2.35% after tax → $11,231 after tax.
• The gap: $206 to I Bonds — tax deferral did the work. The I Bond’s 0.90% fixed beats the TIPS’s 0.50% real yield, and deferring the tax lets the full balance compound.
• The sensitivity: TIPS real yield at 1.8% (a plausible market print) → TIPS win by $376. Inflation at 5% → I Bonds win by $295 (both scale, deferral compounds). Hold 3 years instead of 5 → the 3-month penalty eats the edge and it’s a near tie ($39). Hold 30 years → I Bonds win by $3,645: decades of deferral are the I Bond’s superpower.
• The break-even: at these settings, TIPS need a real yield of 0.97% to tie the I Bond. Above that, TIPS win; below it, I Bonds win. Watch the real yield — it’s the only number that matters.

Output · formula · meaning

3 things investors should know

• The $10,000 cap is the whole game. I Bonds are the better bond per dollar for most savers — but only for the first $10,000 a year per person ($20,000 for a couple, plus $5,000 in paper bonds via the tax refund). Need $100,000 of inflation protection? The first $10k goes to I Bonds and the other $90k has nowhere to go but TIPS. The cap, not the math, decides for big portfolios.
• Phantom income is TIPS’ hidden tax. The inflation adjustment to your TIPS principal is taxed every year even though you don’t receive it until maturity — you need cash from somewhere else to pay it. Inside an IRA the problem vanishes entirely, which is why TIPS belong in tax-advantaged accounts whenever possible. I Bonds sidestep it with deferral instead.
• TIPS can lose money; I Bonds cannot. Sell TIPS before maturity and you get the market price — if real yields rose since you bought, that price is lower. The I Bond composite can never go below 0%, so the principal never falls. If there’s any chance you’ll need the money early, the I Bond’s 12-month lockup is a known cost; the TIPS’s price risk is an unknown one.

Who uses this page

• Emergency-fund builders: the I Bond’s 12-month lockup rules it out for month-one emergencies — but for the deep reserve, 4.26% beats any savings account.
• Pre-retirees and retirees: inflation protection for the bond sleeve — and the IRA question (TIPS go in, I Bonds can’t).
• Parents saving for college: I Bond interest can be federally tax-free for education — but the income limits and registration rules are strict.
• Researchers & students: the Treasury rate figures are public data — cite them with the block below.

Accuracy & limitations

The I Bond composite rate resets every six months — the 4.26% in this page is the May–October 2026 rate, not a promise; future rates follow CPI. The model assumes smooth inflation and holds both rates constant; real TIPS bought on the secondary market have price risk this model doesn’t price (it assumes hold-to-maturity). State and local tax exemption is modeled for both (correct for both bonds). The education tax exclusion, gift-box strategies, and deflation-floor mechanics are not modeled. This is a comparison tool, not financial advice — and it can’t see your liquidity needs, which decide more real-world cases than the math.

Growing the pile itself? Try the compound growth calculator, the no-penalty CD vs savings comparison, and the emergency fund vs invest decision.