# Buffer Calculator

This buffer calculator provides an easy-to-use tool to calculate buffer molarity and prepare buffer solutions using the formula weight of the reagent as well as your desired volume (L, mL, or uL) and concentration (M, mM, or nM).

To calculate the amount of buffer needed, please select the desired buffer from the Selection menu. The empirical formula, pKa, buffer pH range, formula weight and product list will appear. Enter the desired final volume and desired concentration and click “Calculate Mass.”

The exact mass of the buffer will then be calculated in grams and a step-by-step buffer recipe is automatically provided to assist in the buffer preparation process.

Click on the list of product results for more detailed information of our offering of buffers and to order our products.

CAS #:

Empirical Formula:

pKa:

Buffer pH Range:

Formula Weight (g/mol):

Formula weight
g/mol

Desired final volume

Desired concentration

Mass=   g

Error with Formula Weight

Your stock solution of is calculated to be based on the formula weight of g/mol.

To make a solution, add g of to deionized water.

Adjust the final volume of the solution to with deionized water.

Hardly any other substance in chemistry is as controversially discussed as buffers. Determining what is fact and what is fiction can be difficult with the plethora of information that is in circulation. However, one thing is clear: reproducible research is only possible when the results are reliable.

Buffers are commonly used in many different types of scientific studies to maintain or control the acidity of a solution within a desired physiological range, or even to initiate a particular reaction. The pH of substances affects both the rate and efficiency of chemical reactions, and the recovery and purity of products. Hence, buffers considerably contribute to variations in the outcome, and ultimately the success or failure, of studies. Therefore, understanding buffers and error-free calculation of buffers is essential to reduce variability and undesired interactions for reliable research.

What is a buffer solution?

Buffers are aqueous solutions that resist changes in pH, or the acidity or basicity of a solution relative to other substances. The purpose of a buffer in a biological system is to keep the pH (potential hydrogen) constant when there are changes in the hydrogen [H+] ion. Acids give up protons, bases accept them. Buffer solutions are composed of a mixture of weak acid, which acts as a proton donor, and its conjugate base, which acts as an electron acceptor; or a mixture of weak base with a conjugate acid. The buffering of a solution results from two reversible reaction equilibria in a solution wherein the concentration of a proton donor and its conjugate proton acceptor are equal.

Most simple buffers effectively work in the pH scale of pKa ±1. Two common biological buffers are tris(hydroxymethyl)aminomethane (Tris) and 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES).

What is pKa?

The strength of an acid is measured using a pKa value, or the negative log of the acid dissociation constant. A lower pKa value indicates a stronger acid and the greater its ability to donate a proton or fully dissociate in water. The pKa predicts what a molecule will do at a specific pH and is constant for each type of molecule.

How do you determine the pKa of a buffer solution?

pKa values can be determined by titration. A calibrated and automated titrator is used. The free acid of the material to be measured is titrated with a suitable base, and the titration curve is recorded. The pH of the solution is monitored as increasing quantities of a base is added to the solution. pKa is a thermodynamic value and pH is dependent on temperature. The most common pKa constants can be found in this publication1.

What is buffer capacity?

Buffer capacity signifies the ability of the buffer to maintain the pH of a solution and generally depends on the concentration of hydrogen ions in a buffer solution. Buffers that contain higher concentrations offer higher buffering capacity and are lower in pH. However, pKa remains unaffected by concentration. A buffer capacity of 1 means 1 mole of acid or base is added to 1 liter of buffer and the pH changes by 1 unit. The buffer capacity of a mixed weak acid-base buffer is much greater when the individual pKa values are in proximity with each other.

How are buffers classified?

Buffers are typically classified into seven main groups based on the pH range of their effectiveness and can be further delineated by grade. The morpholinic buffers, such as MESMOPS, and MOBS are at the acidic end of the pH scale, ranging from 5.5 to 8.3. Tris is a mid-range buffer stable at pH of 7 to 9.6. Cyclohexylamino buffers, such as CHES and CAPS, are effective at higher pH values from 8.6 to 11.4.