June 2026 CPI 333.952: TIPS Reference CPI for August and September
The Bureau of Labor Statistics reported the June 2026 CPI-U, all items, not seasonally adjusted, at 333.952 (1982 to 1984 = 100). That is a fall of 0.35% from May 2026 and 3.53% above June 2025. This not seasonally adjusted series is the one the Treasury uses to adjust TIPS principal, so the headline seasonally adjusted number in news reports will differ.
The TIPS reference CPI for any day uses the CPI from three months earlier, interpolated toward the value from two months earlier. The June 2026 print fixes every daily reference CPI in August 2026 and the value on September 1, 2026. TIPS principal in June 2026 does not depend on the June 2026 print.
Reference CPI values this print sets
| Date | Reference CPI | Derived from |
|---|---|---|
| August 1, 2026 | 335.12300 | May 2026 CPI |
| August 15, 2026 | 334.59416 | interpolated, day 15 of 31 |
| August 31, 2026 | 333.98977 | interpolated, day 31 of 31 |
| September 1, 2026 | 333.95200 | June 2026 CPI |
Effect on principal
From August 1, 2026 to September 1, 2026, the reference CPI moves down by 0.349%. Every TIPS carries the same index ratio change over those dates, so $10,000 of inflation-adjusted principal on August 1, 2026 becomes about $9,965 on September 1, 2026, before any coupon. A holder in a taxable account owes tax on that principal change for the year even though no cash is paid. See phantom income.
A monthly decline is normal for parts of the year because this series is not seasonally adjusted. Principal on any individual TIPS cannot fall below its original face value at maturity, but it does move down between coupon dates when the reference CPI falls.
The last 12 months
| Month | CPI-U (NSA) | Change | Sets reference CPI for |
|---|---|---|---|
| June 2026 | 333.952 | -0.35% | August 2026 through September 1, 2026 |
| May 2026 | 335.123 | +0.63% | July 2026 through August 1, 2026 |
| April 2026 | 333.020 | +0.85% | June 2026 through July 1, 2026 |
| March 2026 | 330.213 | +1.05% | May 2026 through June 1, 2026 |
| February 2026 | 326.785 | +0.47% | April 2026 through May 1, 2026 |
| January 2026 | 325.252 | +0.37% | March 2026 through April 1, 2026 |
| December 2025 | 324.054 | -0.02% | February 2026 through March 1, 2026 |
| November 2025 | 324.122 | n/a | January 2026 through February 1, 2026 |
| September 2025 | 324.800 | +0.25% | November 2025 through December 1, 2025 |
| August 2025 | 323.976 | +0.29% | October 2025 through November 1, 2025 |
| July 2025 | 323.048 | +0.15% | September 2025 through October 1, 2025 |
| June 2025 | 322.561 | +0.34% | August 2025 through September 1, 2025 |
The BLS published no value for October 2025, so the month is absent from the table and the following month shows no change figure.
Why the three-month lag exists
The Treasury needs a published index value before it can adjust principal, and the BLS publishes each month's CPI about two weeks after the month ends. Using the value from three months earlier and interpolating day by day gives every settlement date a known reference CPI in advance. The lag means TIPS principal always reflects inflation from a few months back, which matters most when inflation changes direction quickly. How TIPS principal and interest work explains the mechanics. The price calculation shows where the index ratio enters a settlement amount.
Sources: BLS series CUUR0000SA0, BLS Consumer Price Index, TreasuryDirect TIPS and CPI data, and the formula in 31 CFR 356, Appendix B. The June 2026 value was first saved by this site on September 11, 2026. Reference CPI figures here are computed from the published index and rounded to five decimals. Treasury's published table governs.
