# How do I do logs with different bases (bases other than 10)

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Most calculators can't do logs in different bases, but you can solve for the answer this way:

Let's say you need to take the log of 5 in base 3. This can also be written as log5 (base 10)/log3 (base 10).

A more technical solution can be found here: http://oakroadsystems.com/math/loglaws.htm#NewBase

Posted on May 25, 2011

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Posted on Jan 02, 2017

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## Related Questions:

### How do I find log with a different base (not 10)?

Calculate the log (base 10) of the number, then divide the result by the log (base 10) of the base.
For example, to calculate the base-3 log of 9, calculate the log of 9 to get 0.954 . Divide that by the log of 3 (about 0.477) to get 2.0 .
Since 9 is 3 squared, the log base 3 of 9 is 2, as we just calculated.

Mar 28, 2012 | Office Equipment & Supplies

Tip

### The Log function!!

I calculators you can't change or set the base of 'log' is default 10 so you need to know these:

log x (base y) = log x / log y

when log x it's automatic log x (base 10) here some examples:

log 8 (base 2) = log 8 / log 2
log 27 (base 3) = log 27 / log 3

and the base it's default 10 again, and that is how you need to use it in calculators(no bases), and here the explanation to this:

log x (base y) = log x (base 10) / log y (base 10) = (log x / log 10) / (log y / log 10) = (log x / log 10) * (log 10 / log y) = log x / log y

here so other stuff about 'log' :

log (x*y) = log x + log y
log (x/y) = log x - log y

Hope it's helped

on Jul 07, 2009 | Casio fx-300ES Calculator

### How to get ans log of bases other then 10

You can calculate the log to any base B by dividing the base-10 log by the log-base-10 of the base B. You can also calculate it by dividing the natural log by the natural log of B.

For example, to calculate the base-3 log of 10, calculate
log(10) / log(3)
or
ln(10) / ln(3)

Jul 20, 2011 | Casio FX-65 Calculator

### How do i do log base x problems (other than log base 10) on the datexx ds 883?

Calculate it the same way as on most other calculators, using the relation

log_b(x) = log(x)/log(b) = ln(x)/ln(b)

In words, calculate the log base 10 of x divided by the log base 10 of the base. You can also use the natural log function instead of the common (base 10) log--just be consistent.

Oct 19, 2010 | DateXX DS-883 Calculator

### How to enter a different log base (other than base e or base 10) into the Texas Instrument TI-80 silver

The TI-83 doesn't have such a function built-in. Use the relationship logb(x) = log(x)/log(b) = ln(x)/ln(b).

May 13, 2010 | Texas Instruments TI-83 Plus Calculator

### How to enter a different log base (other than base e or base 10) into the Texas Instrument TI-80 silver

You cannot. You must use the formula
log_b(a)=ln(a)/ln(b)
where log(a) is common logarithm of a and ln(a)= natural logarithm of a

If you had the TI84PLUS or TI84PLUS SE, you could have installed the newest OS upgrade and that upgrade uses math print which allows the user to calculate logarithms in any base directly.

Mar 22, 2010 | Texas Instruments TI-83 Plus Calculator

### I need help with a change of base formula problem.

It's simple here some logs:

log x base y = log x / log y
log (x*y) = log x + log y
log (x/y) = log x - log y
you just need to know that the default base of log in calculators is 10, so log x mean
log x base 10 = log x / log 10,
so write log x / log y for log x base y example:
log 8 base 2 = log 8 / log 2 that is how you write it on calculator, hope it was helpful

Jul 01, 2009 | Texas Instruments TI-83 Plus Calculator

### How to calculate logarithm values with different base

Like you maybe know in math (I know!) log x base y = log x / log y
so what you need its just input your number (x for example) and log it, than divide log x by log 2.
just: log x / log 2. (by the way in calculator the meaning of log x is log x base 10 the default base is 10)

Jun 05, 2009 | Casio FX-300MS Calculator

### Random based logarithms

to do logarithms with other bases, use change-of-base. let's say you want to do log base 5 of 25. for clarity i'll write this as log(5) 25. you would have to do log(10) 25 / log(10) 5 to get 2. key sequence: [LOG], 2, 5, ), / (divide), [LOG], 5, )

Apr 03, 2009 | Texas Instruments TI-83 Plus Calculator

### How to calculate log value in calculator with different base value

In any scientific calculator log2(n) can be  calculated with either ln or log function as follows

Log2(n)= ln(n) / ln(2)

Or
Log2(n)=log(n) / log(2)

both will give nearly the same answers

Dec 08, 2007 | Casio FX-300MS Calculator

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