PH and POH Calculator + Online Solver With Free Easy Steps

The online pH and pOH Calculator helps you quickly calculate the $ H^{+} $ ions and $OH^{-}$ ions.

The pH and pOH Calculator is useful when working with chemicals. When working in chemistry or other scientific laboratories, scientists need to know the exact value concentration of a chemical.

What Is a PH and POH Calculator?

A pH and pOH Calculator is an online tool that finds the $ H^{+} $ ions in pH and $ OH^{-} $ ions in pOH.

The pH and pOH Calculator needs only one input, either the pH value or the pOH value. The calculator then generates a table representing the hydrogen ion and hydroxide ion concentration.

How To Use a PH and POH Calculator?

You can use the pH and pOH Calculator by entering the pH to pOH values into the specified boxes. The result will be generated when you click the “Submit” button. The step-by-step instructions for using the pH and pOH Calculator are given below.

Step 1

First, you must select the type of value you want to enter. You can do this by clicking on the pH button. A pop-down menu will appear. Select pH or pOH according to your requirement.

Step 2

After selecting the value, you want to input the pH or pOH value in the input box.

Step 3

After you have placed your value, click the Submit button. Your results will appear in a table showing the hydrogen or hydroxide ion concentrations. Below the results, you will also be given the equations used to calculate these concentrations.

How Does PH and POH Calculator Work?

The pH and pOH Calculator works by converting the pH or pOH values into $H^{+} $ ions and  $ OH^{-}$ ions. The calculator also shows the equations used to calculate the hydrogen and hydroxide ions concentrations. pH and pOH values are essential factors in chemical calculations and medicine production. 

The pH and pOH Calculator helps determine how acidic or basic a solution is. 

What Are Acids?

An acid is a molecule that can contribute an $H^{+}$ ion while also remaining energetic after losing that ion. Acids can be identified by their sour taste and turn litmus paper red from blue. Acids are defined in three ways.

The Arrhenius Theory states that acid is a substance or molecule that can donate hydrogen ions in a water solution.

The Brønsted–Lowry Theory states that acids are molecules that donate protons. This took the Arrhenius Theory one step further.

Lewis’s theory defines an acid as a molecule or substance that accepts electrons.

The concentration of hydrogen ions determines the acidity of an acid. The more the hydrogen ions, the more acidic the solution is. This causes the pH value of such acids to be near zero. Hydrochloric acid, Sulphuric acid, and Nitric acid are examples of acids.

What Are Bases?

Bases are molecules that produce hydroxide ions $ (OH^{-}) $ in an aqueous solution. Bases are usually slippery to touch and have a bitter taste. They also turn a red litmus paper blue, one of the key indicators to spot a basic solution. Bases are defined in three different ways.

Arrhenius’s theory defines bases as molecules in a water solution that accepts the hydrogen ions.

Bronsted–Lowry Theory builds on Arrhenius’s idea and defines bases as proton-accepting molecules.

Lewis’s theory suggests bases to be molecules that accept electrons. The hydrogen particle is not mentioned in this definition at all.

The concentration of hydroxide ions that bases produce determines how strong a base is. As the hydroxide ions increase, the base’s strength also increases. Bases tend to have a higher pH value.

Sodium hydroxide, calcium carbonate, and potassium oxide are a few examples of bases.

What Is a PH Scale?

The pH scale (pH) is a numerical scale used to determine how acidic water solutions are. The pH scale is typically ranged from 0 to 14. However, it can exceed these ranges if there is enough basicity or acidity.

The concentration of hydrogen ions in a solution is logarithmically and inversely proportional to pH. The pH to $ H^{+}$ ion is as follows:

\[ pH = -log([ H^{+}]) \]

If the results are less than seven, the solution is considered acidic. However, if the answer is greater than 7, the solution is considered basic or alkaline. Solutions with a pH of 7 are considered to be neutral.

You can also calculate the concentration of hydrogen ions in the solution if you know the pH value. Take a look at the following equation:

\[ [H^{+}] = 10^{-pH} \]

You can utilize pH indicators in addition to the mathematical method of determining pH. The pH test using a litmus paper is a universal test. The litmus paper changes color according to how acidic or basic a solution is.

Our bodies are almost neutral. The pH value of the blood is around 7.4. Only our stomach has a lower pH value, making it acidic to help digest food.

What Is a POH Scale?

The pOH scale is a numerical scale used to measure a solution’s basic level. Like the pH scale, the pOH scale ranges from 0 to 14. The pOH is used to measure the hydroxide ion concentration in a solution. 

pOH can be converted into $ OH^{-} $ ion logarithmically, as shown below:

\[ pOH = -log([ OH^{-}]) \]

The mixture is basic if the solution has a value of less than seven. In contrast, if the solution has a pOH value greater than seven, it is acidic. The neutral value of the solution is seven. We can see that the pOH scale is the opposite of a pH scale.

How To Calculate POH Value?

The pOH value can be calculated using pH or hydrogen ion concentration $ ([H^{+}])$. Both hydrogen ion and hydroxide ion are co-related by the following equation:

\[ [OH^{-}] = \frac {K_{w}} {[H^{+}]} \]

Here, Kw is the water ionization constant. Now we apply logarithm to both sides and get:

pOH = pKw – pH  

We get an approximation of the value of pOH. 

 pOH = 14 – pH

This is how you calculate the value of pOH.

Solved Example

Here are some examples of finding the ion concentration using the pH and pOH Calculator

Example 1

Find the $ H^{+} $ concentration in a solution with pH = 4.


First, select the pH mode, then input the pH value = 4. After inputting the pH value, we click the “Submit” button, and we are presented with a table showing the results concentration of hydrogen ions. The results are represented below:

Hydrogen ion concentration:

\[ H^+  = 100 \frac {\mu mol}{L} (micromoles \ per \ liter),\]

Can be expressed in $millimoles per cubic meter$ as:

\[H^+ = 100 \frac {mmol}{m^{3}} (millimoles \ per \ cubic \ meter),\]

Concentration expressed in moles per cubic meter:

\[H^+ = 0.1 \frac {mol}{m^{3}} (moles per \ cubic \ meter)\]

Example 2

Presented with a solution with pH = 8, find the concentration of $ H^{+} $ ions in the solution.


First, we select the pH mode in our calculator to solve this problem. Then we type in our pH value provided in the question above pH = 8. After typing our value, we click the “Submit” button. We are presented with the hydrogen ion concentration as shown below.

Hydrogen ion concentration:

\[H^+ = 10 \frac { nmol}{L} (nanomoles\ per \ liter),\]

\[H^+ = 0.01 \frac {mmol}{m^{3}} (millimoles\ per \ cubic \ meter),\]

\[H^+ = 10 \frac {n}{M} (nanomolar)\]

Example 3

A chemistry teacher wants to find the $[OH^{-}] $ ion concentration of a solution with a pOH = 5. Calculate the hydroxide ion concentration in the solution.


We must first set our calculator to pOH mode to calculate the hydroxide ion concentration. We then plug in the pOH value as provided above. After inputting the pOH value, we click the “Submit” button. We are presented with the hydroxide ion concentration in the solution, as shown below.

Hydrogen ion concentration:

\[H^+ = 10 \frac {\mu mol}{L} \text{(micromoles per liter)},\]

\[H^+ = 10 \frac {mmol}{m^{3}} \text{(millimoles per cubic meter)},\]

\[H^+ = 0.01 \frac {mol}{m^{3}} \text{(moles per cubic meter)}\]

Example 4

A cleaning company releases an all-purpose cleaner with a pOH value of 2. Calculate the hydroxide ion concentration in the cleaning product.


To find the hydroxide ion concentration, we must first select the pOH value in the calculator, then we enter our pOH value. After entering the pOH value, we click the “Submit” button. This generates a table containing the hydroxide ion concentration of the solution. You can look at the results below:

Hydrogen ion concentration:

\[H^+ = 10 \frac { mmol}{L} \text{(millimoles per liter)},\]

\[H^+ = 0.01 \frac {mol}{L} \text{(mole  per liter)},\]

\[H^+ = 10 \frac {m}{M} (millimolar)\]

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