TI BAII Plus Frequently Asked Questions

Over the years, I have received many questions about financial calculators. I will compile a list of the most frequently asked questions here.

Q: My BAII Plus is showing a comma instead of a decimal point. How do I fix this problem?

A: This is easily the most commonly asked question. I wish I knew how people got themselves into this situation, because it seems unlikely that it could happen by accident. Here is how to solve the problem: Press 2nd . then ⯆ (down arrow) three times. Now, press 2nd ENTER to switch between US and EUR.

A little background on this. In the U.S. and many other countries, we use a decimal point as the radix point (or decimal separator) and a comma as the thousands separator. Many other countries do exactly the opposite. For a complete list, see the decimal separator article on Wikipedia. Interestingly, as far as I can tell this has nothing to do with the side of the road on which you drive. Obviously, the BAII Plus was created with worldwide users in mind.

Q: How do I change the number of decimal places that are displayed?

A: Simply press 2nd .. Now, DEC will appear on the screen. Press a number key and then ENTER. For example, to display five decimal places, press 2nd . 5 ENTER.

Q: How do I enter a negative number into one of the TVM keys on the BAII Plus?

A: The way to do it is by using the +|- (change sign) key. For example, to enter -1,000 into FV, press 1000 +|- FV.

Q: How can I edit the cash flows that I have entered into the CF key?

A: Great question because we all make mistakes, and it would be a pain to have to re-enter all of the cash flows. Just go back into the cash flow list by pressing CF. Now use the up or down arrow keys to go to the cash flow (or frequency) that you wish to change. Enter the new number and press ENTER.

Q: How do I find roots other than square roots using the BAII Plus?

A: In finance it seems that we are forever calculating various roots (cube root, fourth root, 365th root, etc). Fortunately, this is pretty simple to do if you can remember a simple mathematical rule:

$$\sqrt[N]{X} = {X^{\frac{1}{N}}}$$

So, to calculate the 5th root of 100, we simply raise 100 to the 1/5th power. To do this: 100 y^x 5 1/x =. In this example, the 5th root of 100 equals 2.51189. Using this technique you can calculate any root.

Q: My calculator only has a key to calculate natural logarithms. How do I calculate logarithms to other bases (say, base 10)?

A: Most often, in finance, we typically use natural logarithms (base e), usually abbreviated as $Ln\left( X \right)$. However, sometimes we need to use other bases. Converting from base e to any other base can be done with the following formula (I’m converting to base 10):

$$Lo{g_{10}}\left( X \right) = \frac{{Ln\left( X \right)}}{{Ln\left( {10} \right)}}$$

So, just calculate the natural log of your number, and then divide it by the natural log of the new base. For example, Log10(3) = Ln(3)/Ln(10) = 0.478.

Q: What battery does the TI BAII Plus use, and how do I change it?

A: The TI BAII Plus uses a single CR 2032 battery (the link goes to Amazon.com), like many other calculators. To change the battery, you will need a small Phillips head screwdriver like you would find in an eyeglass repair kit. After removing the four screws on the back, you will need to carefully pry the back cover from the calculator. This, at least on mine, can be a bit difficult, but it will come off. You will need something to pry with (a tiny flat-head screwdriver works well). Now, you can replace the battery, but be careful to place the new one in the same orientation as the original.

Q: How do I reset the TI BAII Plus?

A: There are two ways to reset the calculator. You should only do this in case the calculator malfunctions. Most problems are due to user error, but there certainly are times that call for a factory reset.

Reset Method 1: Press 2nd +|- (that is RESET) and then ENTER. That should clear everything out. Then press 2nd CPT (QUIT). You may have to reset some things like the number of decimal places.

Reset Method 2: There is a recessed button on the back of the calculator. You can press it with a pencil or paperclip. This is a hard reset that should return everything to original factory settings.