Series I Savings Bond fixed base-rates

Sunday, November 1st, 2015
Categorized as: Series I US Savings Bonds

The Treasury sets the Series I Savings Bond fixed base-rate administratively, which means the criteria it uses aren’t public information.

Because all I bonds receive the same inflation component, what makes one I bond better than another is the fixed base-rate. Since I bonds were introduced, the fixed base-rate has varied from a low of 0.0% (yeah, zero) to a high of 3.6%.

New fixed base-rates are announced at the beginning of May and November each year and apply to new Savings Bonds issued during the following six-month period. Once an I bond is issued, its fixed base-rate never changes.

The following graph shows the historical level of the I bond fixed base-rate in red. It also shows rates for TIPS, the Treasury’s other inflation-protected security, which is traded in the open market.

Because they are traded, the rates of TIPS change daily. The Treasury publishes daily data on TIPS interest rates. This data goes back to January 2, 2003 for 5-year and 10-year TIPS, and to July 27, 2004 for 20-year TIPS. Each Friday’s figure is shown as a data point in the following graph.

For data before 2003, the graph shows the yield of each TIPS on the day it was issued. This data series is a mix of 5, 10, and 30-year TIPS.

The table that follows gives the exact fixed base-rate for all Series I Savings Bonds. It also shows the 10-year TIPS rate on the day before the announcement and the difference in basis points (hundredths of a percent) between the two rates.


Series I Savings Bond fixed base-rates

Issue Date Fixed Rate 10-yr TIPS difference
Sep 98 – Oct 98 3.40% n/a
Nov 98 – Apr 99 3.30% n/a
May 99 – Oct 99 3.30% n/a
Nov 99 – Apr 00 3.40% n/a
May 00 – Oct 00 3.60% n/a
Nov 00 – Apr 01 3.40% n/a
May 01 – Oct 01 3.00% n/a
Nov 01 – Apr 02 2.00% n/a
May 02 – Oct 02 2.00% n/a
Nov 02 – Apr 03 1.60% n/a
May 03 – Oct 03 1.10% 2.16% 106
Nov 03 – Apr 04 1.10% 1.97% 87
May 04 – Oct 04 1.00% 2.11% 111
Nov 04 – Apr 05 1.00% 1.63% 63
May 05 – Oct 05 1.20% 1.61% 41
Nov 05 – Apr 06 1.00% 2.00% 100
May 06 – Oct 06 1.40% 2.39% 99
Nov 06 – Apr 07 1.40% 2.34% 94
May 07 – Oct 07 1.30% 2.25% 95
Nov 07 – Apr 08 1.20% 2.14% 94
May 08 – Oct 08 0.00% 1.50% 150
Nov 08 – Apr 09 0.70% 3.14% 244
May 09 – Oct 09 0.10% 1.69% 159
Nov 09 – Apr 10 0.30% 1.41% 111
May 10 – Oct 10 0.20% 1.29% 109
Nov 10 – Apr 11 0.00% 0.50% 50
May 11 – Oct 11 0.00% 0.75% 75
Nov 11 – Apr 12 0.00% 0.08% 8
May 12 – Oct 12 0.00% -0.30% -30
Nov 12 – Apr 13 0.00% -0.78% -78
May 13 – Oct 13 0.00% -0.64% -64
Nov 13 – Apr 14 0.20% 0.40% 20
May 14 – Oct 14 0.10% 0.49% 39
Nov 14 – April 15 0.00% 0.49% 49
May 15 – Oct. 15 0.00% 0.31% 31
Nov 15 – April 16 0.10% 0.38% 28
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FDIC Insured Certificates of Deposit can pay 1 or 2% more than savings bonds when held for a similar length of time. See top CD Rates Below:


On April 17th, 2006 Dan said:

Interesting stuff!

As far as I can see, the fixed rate has really seemed correlated to TIPS rates until last November’s decision to go lower.

I imagine TIPS and I-Bonds usually aren’t competing for personal investors’ money, as seems to have advantages for tax-deferred accounts and the other for taxable. But with the spread widening, maybe more taxable investors will buy TIPS instead of I-Bonds if the Treasury fails to raise the fixed rate again?

On April 17th, 2006 Mario said:

I imagine the Treasury probably has a specific sales volume of I bonds in mind that it wants to achieve, and it sets the fixed rate based on it.

Now, in a period where the inflation component closely tracks average CPI-U changes, as is usually the case, the fixed rate probably will correlate well with TIPS, since they are the market-based counterpart.

On the other hand, in a period where the inflation component is way off created by sudden spikes (like the current and next periods), it makes sense that the fixed rate would have to not correlate with TIPS, since the spike it TIPS would have been short lived.

Of course, the impact of the fixed rate on the 30 year life of the bond also has to figure into the equation, not just the current sales period.

On April 18th, 2006 Nico said:

It seems like the Treasury has every opportunity to slight I-Bond purchasers if they choose to.

They can set the fixed rate to any value they want, and don’t have to reveal their algorithm or their logic. They could just as well set it to 0% and be done with it.

The treasury has already signaled that selling savings bonds isnt a high priority for it. They make most of their funds on open market bonds, and would probably prefer to dump the administrative costs of this program.

I think it would be great if we could lobby congress to set a mandatory formula for the fixed rate.

On April 18th, 2006 Dan said:

I’ve scheduled my 5-yr TIPS purchase for Thursday’s auction on Treasury Direct, to make up for all of the I-bonds I haven’t been buying the last six months. (In my opinion, CPI + 2%+ interest without tax deferral easily beats CPI + 1% with tax deferral.)

Hopefully, the next fixed rate will make I-bonds attractive again. Otherwise, there’s always the July TIPS auction…

On April 18th, 2006 Tom Adams said:

Dan – one other thing TIPS investors need to be aware of is that if they need to redeem before the security matures, there’s the possibility of capital losses (or gains).

When interest rates go up, the value of bonds goes down and vice versa.

On the other hand, the TIPS offering later this month is a 5-year security. The interest-rate caused value swings are a bigger problem with the longer term (10-year, 20-year) TIPS than with this one. And since the market isn’t giving a premium right now for longer terms, the 5-year TIPS looks pretty good.

Also, just to clarify, Thursday (April 20) is just the official annoucement date – when the Treasury announces for sure whether the securities will be available. The actual deadline for investing in these securities on TreasuryDirect will probably be the morning of Tuesday 4/25. The actual issue date will probably be Friday, 4/28.

On April 21st, 2006 Dan said:


Thanks – very important point. Any readers considering a TIPS purchase as an alternative to I-bonds should consider those differences!

In my case, my small monthly contributions to I-Bonds were used as an inflation-indexed emergency fund (after 12-mo holding period). But instead I’ve been leaving that money in an online savings account ever since the fixed rate went south this last time, and it is this money that I plan to use for TIPS. If an emergency should happen that makes me redeem the TIPS early, I’d be stuck with any market price fluctuations plus TD’s secondary market fee, which if I remember correctly is $45.

On July 17th, 2007 Ethan said:

So, if the rule of thumb continues to work, perhaps we will see a 1.70% fixed rate at the next adjustment on Nov. 1?

On July 17th, 2007 Tom Adams said:

Ethan – perhaps is the critical word. It depends what happens to the TIPS rate between now and then.

Tom Adams

On October 11th, 2007 Ethan said:

So, given the 10-year TIPS rate of 2.36% and applying the Tom Adams Rule of Thumb, do we all guess that the fixed portion of the Nov. 1 I-Bond will be up to 1.40%?

On October 12th, 2007 Ethan said:

Or, to put it another way, do we all agree that the fixed portion will either remain the same or go up to 1.40%?

On October 12th, 2007 Tom Adams said:

Hi Ethan – Yes, but….

The rates could still change between now and the end of October. You can follow changes in the 10-year TIPS rate daily on the Treasury’s web site.

Tom Adams

On October 12th, 2007 Ethan said:


You sure are right, given the recent volatility. Thanks for the link. Gee, I wonder when the new rate gets decided. I know it is published 11/1, but when do they close the books and make the decision? I guess we will never know.

On October 12th, 2007 Tom Adams said:

Ethan – In the chart above I show the price on the day previous to the announcement – in other words, the most recent daily price they have when they make the announcement. But there’s nothing that says that’s what they have to use.

Tom Adams

On May 4th, 2008 Nik said:

It is interesting to note the direct correlation between the graphic fall of I bond rates which begin in the year 2000, and the election of the current administration that same year.

On May 9th, 2008 Richard Hetrick said:

Tom. i have some ee bonds 01/2003 would it be worth it to trade them in for i bonds? the intrest on them is not looking good. or should i let them ride? i will to november anyway

On May 12th, 2008 Tom Adams said:

Richard – 1/03 EE bonds are better choice than I bonds with a 0% fixed rate.

Tom Adams

On October 12th, 2008 Mike said:

I was leaning toward buying some I-bonds before the end of October. But I was assuming that the fixed rate would stay the same in the next period. The 10-year TIPS rate is now almost 3%. I still think the fixed rate might stay at 0, since the Treasury doesn’t seem too interested in selling I-bonds, and the inflation component should be good (we’ll know on Thursday). Any guess as to what the new fixed rate will be?

On October 13th, 2008 Tom Adams said:

Hi Mike – I’m wondering about this the same as you. TIPS rates exploded last week. If they stay this high, we could see the highest I bond fixed rate in years. We could also see the Treasury leave the rate at zero. You can’t depend on them to follow the plan anymore.

Tom Adams

On January 26th, 2009 Don Wilson said:

With CD rates low today and the fixed rate on I Bonds low, which is the better buy? Or another alternative?

On January 27th, 2009 Tom Adams said:

Hi Don – Sorry, I don’t know. No one will know until about the time the CDs mature. How about some of each?

Tom Adams

On January 28th, 2009 Don Wilson said:

Thank you Tom, Another question-is there any value in buying some I bonds just before the fixed rate change and again just after the change?

On January 29th, 2009 Tom Adams said:

Don – when you have a choice between two things and you don’t know which is better, the safest thing to do is some of each. You’ll get neither the best or worst result. Note this option isn’t possible if your choice is two doors, but it is possible with two different issues of Savings Bonds or with Savings Bonds and CDs.

Tom Adams

On February 2nd, 2009 Don Wilson said:

Thnaks Tom, That sounds reasonable. I appreciate your comments and your work on this site. Very informative.

On April 15th, 2009 ian wilson said:

We are very close to the may fixed rate change for I bonds. What is your best guess at this point? I realize its just your best guess but your insight is better than none.

On April 16th, 2009 Tom Adams said:

Ian – my best guess is that it will be in the 0.5% to 1.0% range. In other words, it might go up, it might go down, or it might stay the same old 0.7%.

Tom Adams

On July 14th, 2009 J. McCormick said:

I’m confused. Which is the better buy at this
time…EE or I bonds?

On July 15th, 2009 Tom Adams said:

J – right now neither EE or I bonds are very interesting as an investment.

In general, however, I bonds earn more than EE bonds. The Treasury is just taking advantage of people with EE bonds.

Tom Adams

On August 5th, 2009 Stansel Harvey said:

Beware: The fixed rate component of the I Bonds is not fixed. It can go down. With the flexible rate portion in negative territory it pulls down the fixed rate. Most all of my previously purchased I Bonds are drawing 0% interest in spite of them having a good “fixed” rate of return. So, when is a fixed rate not a fixed rate? When the government runs the program.

On August 6th, 2009 Tom Adams said:

Stansel – It’s not correct to say “The fixed rate component of the I Bonds is not fixed.”

It’s fixed, and the inflation component is added to or subtracted from it, depending on whether the inflation component is positive or negative. That’s how I bonds have always worked and have always been described on this web site.

The inflation component was just never negative before. I don’t see how it’s the government’s fault that you didn’t understand how the investment you bought worked. The Treasury was very clear about it working this way when you invested in the I bonds.

Tom Adams

On December 21st, 2009 Pat Johnson said:

I have a new granddaughter and was thinking of getting her savings bonds. is this a good idea of should I look at something else.

On December 22nd, 2009 Tom Adams said:

Pat – After answering five years worth of questions about various aspects of children and parents fighting over Savings Bonds, I am not fond of using them as gifts. But if you’re still interested, see my page on gift bonds.

Tom Adams

On March 27th, 2010 Paul said:

Hello! I’m trying to write my own calculator for I-Series bonds, but I can’t get my results the match the calculator on the TreasuryDirect website and the official redemption tables. There’s always a small difference and I can’t figure out how TD gets its results. Have you figured it out?

On March 29th, 2010 Tom Adams said:

Paul – the info you’re looking for is here. If you still have questions, please ask them on that post.

Tom Adams

On March 31st, 2010 Paul said:

Thanks, those instructions were exactly what I needed.

On April 1st, 2010 Lisa said:

Hi Tom – In the fixed rate section there was a link to the Treasury daily TIPS interest rates back to 2003. This was helpful for looking at the fixed rate trends. The link is now referencing different rate data. Can you restore the original link?

On April 1st, 2010 Tom Adams said:

Lisa – The page you’re looking for is here, but it’s much harder to fish the daily TIPS data from that page than from the new link. The new link also goes back to 2003, just click where it says Historical Data at the upper-right.

Tom Adams

On April 1st, 2010 Lisa said:

Thanks Tom. This is a great website.

On May 7th, 2010 kevin said:

Tom, my 401k just started offering a tips fund, do you think this is a good place to start investing some of my contibutions?

On May 7th, 2010 Tom Adams said:

Kevin – Yes, I think a TIPS fund is an appropriate place for a portion of your contributions. TIPS funds have done quite well in the past, although that in itself doesn’t mean they will do so in the future.

There’s some risk that the government might partially default on these someday, but if that happens I have no idea what you should have invested your 401K funds in instead, as everything else will perform as badly or worse.

Tom Adams

Comments Closed

June 1, 2010

After six years, over 400 posts, 3,680 real comments, and over 90,000 spam comments (thank you, Akismet, for making managing a blog with comments possible), I am closing public comments on I will contine to update the main articles on this site, but not the comments.

Virtually every question about Savings Bonds has been asked and answered on this site multiple times. Use the search feature (see the box in the gray area near the top of this page) or the detailed menu on the lower part of the home page to find the information you're looking for. If you have a copy of Savings Bond Advisor, you can ask me a question here.

Tom Adams

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