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Buffer Calculator

Buffer preparation.  Below is a simple excel based calculator you can use to calculate how much of your weak acid and conjugate base you need to add to make a buffer.  Simply enter all relevant information.  Remember that a good buffer has a pKa within 1 pH of the target pH -otherwise you'll be trying to weigh out something like 0.0000005 grams.

Please note, there are other ways to make buffers, this calculator just does the equilibrium math for you if you have both your acid and your conjugate base available. For more information on the math actually being done, please see the Buffer page.  The basic equation used is the Henderson-Hasselbalch equation solved for [A]

You must enter your target pH, your Ka or pKa, the desired concentration of the acid form of the buffer, and either the molecular weights of your acid and base, or their concentration in solution.  You also have to tell it how much buffer solution you want.

*You need to be using the latest Internet Explorer with all the updates to use this file.  You can also download the file to use offline.

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If you would like to see a much more complete and complicated free excel buffer calculator - I would recommend this site.  I have to warn you though that you really need to know what you are doing in order to use that one.  The calculator above, or the solved Henderson-Hasselbalch equation should be enough for most people's purposes.


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