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Series I Savings Bonds Rates & Terms: Calculating Interest Rates on I Bonds

What interest will I get if I buy an I bond now?

The composite rate for I bonds issued from May 1, 2015, through October 31, 2015, is 0.00%. This rate applies for the first six months you own the bond.

How do I bonds earn interest?

An I bond earns interest monthly from the first day of the month in the issue date. The interest accrues (is added to the bond) for up to 30 years.

  • The interest is compounded semiannually. Every six months from the bond's issue date, all interest the bond has earned in previous months is in the bond's new principal value. Interest is earned on the new principal for the next six months. For example, in month seven, interest is earned on the original price plus six months of interest. In month 13, interest is earned on the original price plus 12 months of interest. (However, values displayed by the Savings Bond Calculator for bonds that are less than five years old do not include the latest three months of interest. These values reflect the interest penalty.) If you hold the bond for at least five years, when you cash in (redeem) the bond, you receive all the interest the bond has earned plus the amount you paid for the bond.
  • You can redeem the bond after 12 months. However, if you redeem the bond before it is five years old, you lose the last three months of interest.

How does Treasury figure the I bond interest rate?

The interest on I bonds is a combination of

  • a fixed rate, and
  • an inflation rate

To see the current value of your bonds, use the Savings Bond Calculator. When using the Savings Bond Calculator to look up values of bonds that are less than 5 years old, keep in mind that the values of those bonds do not include the latest three months of interest. However, rates shown by the Savings Bond Calculator for those bonds do not reflect that interest penalty.

Fixed rate

You know the fixed rate of interest that you will get for your bond when you buy the bond. That fixed rate does not change during the life of the bond.

Treasury announces the fixed rate for I bonds every six months (on the first business day in May and on the first business day in November). That fixed rate then applies to all I bonds issued during the next six months.

The fixed rate is an annual rate. Compounding is semiannual.

Inflation rate

Unlike the fixed rate which does not change for the life of the bond, the inflation rate can and usually does change every six months.

We set the inflation rate every six months (on the first business day of May and on the first business day of November), based on changes in the non-seasonally adjusted Consumer Price Index for all Urban Consumers (CPI-U) for all items, including food and energy.

However, the change is applied to your bond every six months from the bond's issue date.  (The dates for these changes might not be May 1 and November 1.) When does my bond change rates?

Combining the two rates

To get the actual rate of interest (sometimes referred to as the composite or earnings rate) we combine the fixed rate and the inflation rate, using the equation in the example below.

  • The combined rate will never be less than zero. However, the combined rate can be lower than the fixed rate. If the inflation rate is negative (because we have deflation, not inflation), it can offset some of the fixed rate.
  • If the inflation rate is so negative that it would take away more than the fixed rate, we don't let that happen. We stop at zero.

An example

The composite rate for I bonds issued May 1, 2015 – October 31, 2015, is 0.00%
Here's how we set that composite rate:
Fixed rate 0.00%
Inflation rate -0.80%
Composite rate = [fixed rate + (2 x inflation rate) + (fixed rate x inflation rate)] [0.0000 + (2 x -0.0080) + (0.0000 x -0.0080)]
Composite rate [0.0000 + -0.0160 + 0.0000000]
Composite rate -0.016
Composite rate 0.00%
(When the calculation produces a negative number, we set the rate at 0.00%.)

When does my bond change rates?

Issue month of your bond New rates take effect
January January 1 and July 1
February February 1 and August 1
March March 1 and September 1
April April 1 and October 1
May May 1 and November 1
June June 1 and December 1
July July 1 and January 1
August August 1 and February 1
September September 1 and March 1
October October 1 and April 1
November November 1 and May 1
December December 1 and June 1

Because I bonds that are less than five years old have values that do not include the latestthree months of interest, values displayed by the Savings Bond Calculator for these bonds will not reflect rate changes on the schedule in the table above (When does my bond change rates?) When looking at changes in values for these bonds, rate changes will seem to be delayed by three months.

What have rates been in the past?

Our Series I bond rate chart shows in one table all past and current rates--fixed rates, inflation rates, and composite rates.

The two tables below show fixed rates and inflation rates, respectively.

Fixed rates

The fixed rate set each May and November applies to all bonds we issue in the six months following the date when we set the rate. The fixed rate applies for the life of the bond.

Date the fixed rate was set Fixed rate for bonds issued in the six months after that date
May 1, 2015 0.00%
November 1, 2014 0.00%
May 1, 2014 0.10%
November 1, 2013 0.20%
May 1, 2013 0.00%
November 1, 2012 0.00%
May 1, 2012 0.00%
November 1, 2011 0.00%
May 1, 2011 0.00%
November 1, 2010 0.00%
May 1, 2010 0.20%
November 1, 2009 0.30%
May 1, 2009 0.10%
November 1, 2008 0.70%
May 1, 2008 0.00%
November 1, 2007 1.20%
May 1, 2007 1.30%
November 1, 2006 1.40%
May 1, 2006 1.40%
November 1, 2005 1.00%
May 1, 2005 1.20%
November 1, 2004 1.00%
May 1, 2004 1.00%
November 1, 2003 1.10%
May 1, 2003 1.10%
November 1, 2002 1.60%
May 1, 2002 2.00%
November 1, 2001 2.00%
May 1, 2001 3.00%
November 1, 2000 3.40%
May 1, 2000 3.60%
November 1, 1999 3.40%
May 1, 1999 3.30%
November 1, 1998 3.30%
September 1, 1998 3.40%

Inflation rates

The inflation rate set each May and November applies for six months to all I bonds ever issued.

Date the inflation rate was set Inflation rate for six months
(See: When does my bond change rates?)
May 1, 2015 -0.80%
November 1, 2014 0.74%
May 1, 2014 0.92%
November 1, 2013 0.59%
May 1, 2013 0.59%
November 1, 2012 0.88%
May 1, 2012 1.10%
November 1, 2011 1.53%
May 1, 2011 2.30%
November 1, 2010 0.37%
May 1, 2010 0.77%
November 1, 2009 1.53%
May 1, 2009 -2.78%
November 1, 2008 2.46%
May 1, 2008 2.42%
November 1, 2007 1.53%
May 1, 2007 1.21%
November 1, 2006 1.55%
May 1, 2006 0.50%
November 1, 2005 2.85%
May 1, 2005 1.79%
November 1, 2004 1.33%
May 1, 2004 1.19%
November 1, 2003 0.54%
May 1, 2003 1.77%
November 1, 2002 1.23%
May 1, 2002 0.28%
November 1, 2001 1.19%
May 1, 2001 1.44%
November 1, 2000 1.52%
May 1, 2000 1.91%
November 1, 1999 1.76%
May 1, 1999 0.86%
November 1, 1998 0.86%
September 1, 1998 0.62%

What is the current composite rate for my I bond?

Composite rates--Current

The table below shows the current composite rate for all I bonds.  (See “When does my bond change rates?”) Each composite rate applies for six months.

Period when you bought
your I bond
Composite rate for your six-month earning period starting during May-October 2015
(See “When does my bond change rates?”)
From Through  
May 2015 Oct. 2015 0.00%
Nov. 2014 Apr. 2015 0.00%
May 2014 Oct. 2014 0.00%
Nov. 2013 Apr. 2014 0.00%
May 2013 Oct. 2013 0.00%
Nov. 2012 Apr. 2013 0.00%
May 2012 Oct. 2012 0.00%
Nov. 2011 Apr. 2012 0.00%
May 2011 Oct. 2011 0.00%
Nov. 2010 Apr. 2011 0.00%
May 2010 Oct. 2010 0.00%
Nov. 2009 Apr. 2010 0.00%
May 2009 Oct. 2009 0.00%
Nov. 2008 Apr. 2009 0.00%
May 2008 Oct. 2008 0.00%
Nov. 2007 Apr. 2008 0.00%
May 2007 Oct. 2007 0.00%
Nov. 2006 Apr. 2007 0.00%
May 2006 Oct. 2006 0.00%
Nov. 2005 Apr. 2006 0.00%
May 2005 Oct. 2005 0.00%
Nov. 2004 Apr. 2005 0.00%
May 2004 Oct. 2004 0.00%
Nov. 2003 Apr. 2004 0.00%
May 2003 Oct. 2003 0.00%
Nov. 2002 Apr. 2003 0.00%
May 2002 Oct. 2002 0.38%
Nov. 2001 Apr. 2002 0.38%
May 2001 Oct. 2001 1.38%
Nov. 2000 Apr. 2001 1.77%
May 2000 Oct. 2000 1.97%
Nov. 1999 Apr. 2000 1.77%
May 1999 Oct. 1999 1.67%
Nov. 1998 Apr. 1999 1.67%
Sept. 1998 Oct. 1998 1.77%

Where can I find more information on rates?

Our Series I bond rate chart shows in one table all past and current rates--fixed rates, inflation rates, and composite rates.