Sure, savings bonds aren't likely to outstrip the gains you can make in a diversified portfolio of stocks, over the long run. But they can certainly let you sleep while the stock market takes some volatile swings in the short run.

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I Bond Rates

The rate of an I bond is based on two separate rates, one of which remains constant for the life of the bond, and another linked to changes in the CPI-U measurement. The composite I bond rate changes every 6 months from the issue date to reflect the change in inflation.

Current I Bond Rate for a new bond:

Current rates for a new bond. Valid November 2014 - April 2015

  • Fixed rate: 0.00%
  • Semi-annual CPI-U change: 0.74%
  • Variable rate: 1.48%
  • Composite rate: 1.48%

Next I bond rate

The next I bond rate change will be on May 1, 2015

  • The fixed rate of a new bond is unknown until the start of the next semiannual period.
  • The inflation-linked rate is based on the CPI-U changes. Nov. Rate:
    March April May June July Aug. Sept.
    236.293 237.072 237.900 238.343 238.250 237.852 238.031


    May Rate:
    Sept. Oct. Nov. Dec. Jan. Feb. Mar.
    238.031



Composition of the I Bond Rate

I Bond rates are based on two factors: the fixed rate and the inflation-linked variable. The fixed rate is established by the Treasury Department by an unknown process. The inflation-linked rate is based on the rate of inflation over the past 6 months as measured by the CPI-U. The two rates are used in a formula to determine the composite rate of the I Bond. Every six months from the purchase month, an I Bond's rate will change based on the new inflation value. The fixed rate will remain the same throughout the life of the bond.

IBond interest rates are composed of a fixed rate and CPI-U based rate.

I Bond Rate Forumula to Determine the Composite Rate
Composite Rate = Fixed rate + 2 * CPI-U Rate +
(Fixed rate * CPI-U Rate)


I Bond Rate Change Effective Date

The composite rate of a bond will change every 6 months based on the changes in inflation. Since every bond must have 6 full months with the inflation-linked rate active, the composite rate of a bond will not change to reflect the new inflation-linked rate until that bond's six month anniversary. The following chart shows when a bond will change rates for the May and November adjustments based on the issue month of the bond.

Bond Issue Month May rate goes into effect Nov. rate goes into effect
January July 1 January 1
February August 1 February 1
March September 1 March 1
April October 1 April 1
May May 1 November 1
June June 1 December 1
July July 1 January 1
August August 1 February 1
September September 1 March 1
October October 1 April 1
November May 1 November 1
December June 1 December 1

Example: An I bond purchased in October will begin with a composite rate based on the fixed rate and inflation-linked rate announced in May. On November 1st, the new inflation data is released, but the bond has not reached the six month anniversary, so the rate will not change. On April 1, the October I Bond will change to reflect the new inflation-linked rate announced in November, but will maintain the same fixed rate it had in October. The new composite rate will be comprised of the fixed rate from when the bond was purchased and the inflation-linked rate announced in November. In May, the inflation data will again be announced, but that rate will not go into effect for this October-issued bond until October.

I Bond Rate Calculator

Use this calculator to calculate an I bond's rate. Enter the CPI-U growth rate and the fixed rate you think will be chosen to calculate the I bond's new rate.

I Bond Rate Calculator
Composite Rate = Fixed rate + 2 * CPI-U Rate + (Fixed rate * CPI-U Rate)

CPI-U Increase in %
Fixed Rate in %
New I Bond Rate would be:





Page last modified 11/3/2014