How to Enter Logarithms on Your Graphing Calculator

Filed under Difficulty: Easy, TI-83 Plus, TI-84 Plus, TI-89, TI-92 Plus.

Most graphing and scientific calculators have the ability to calculate logarithms, but you might come across questions which require you to use a different base than your calculator’s built-in functions. Thankfully, there is a simple formula called the “change of base” formula that allows you to calculate any logarithm on your calculator:

logarithm base change1 How to Enter Logarithms on Your Graphing Calculator

Your calculator may have simply a ln( or log( button, but for this formula you only need one of these:

logarithm base change2 How to Enter Logarithms on Your Graphing Calculator

For example, to evaluate the logarithm base 2 of 8, enter ln(8)/ln(2) into your calculator and press ENTER. You should get 3 as your answer. Try it for yourself!

log change of base How to Enter Logarithms on Your Graphing Calculator

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