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pH Calculator

Select the calculation parameters and enter their values. The calculator will readily calculate the pH, pOH, H+, and OH- ions in an acidic or basic solution.

molars (M)

millimolars (mM)

micromolars (µM)

nanomolars (nM)

picomolars (pM)

femtomolars (fM)

attomolars (aM)

zeptomolars (zM)

nanograms (ng)

micrograms (µg)

milligrams (mg)

grams (g)

decagrams (dag)

kilograms (kg)

tons (t)

grain (gr)

dram (dr)

pounds (lbs)


troy ounces (oz t)

ounces (oz)

cubic millimeters (mm³)

cubic centimeters (cm³)

cubic decimeters (dm³)

cubic meters (m³)

cubic inches (in³)

cubic feet (ft³)

milliliters (ml)

centiliters (cl)


US gallons (US gal)

UK gallons (UK gal)

US fluid ounces (US fl oz)

UK fluid ounces (UK fl oz)

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Let this free pH calculator calculate pH by using either concentration, volume, or weight method. You must be thinking how. Do not worry! Let’s move forward without wasting moments! Stay with us!

What Is pH?

In the light of chemistry world: “pH is the potential of hydrogen ions” Basically, pH indicates how much hydrogen ions are active there in the aqueous solution. You can also consider it as the concentration of the hydrogen ions in the liquid. pH seems like a periodic element but it is not. In fact, it is a unit of measurement.

pH Formula:

You can calculate pH from the following formula:

pH = −log[H+]

H+ Ions Formula:

From the above formula of pH, you can go for pH conversion to the hydrogen ions as bellow:

H+ = 10^-pH

The free online pH formula calculator also makes use of the above couple of formulas to calculate pH instantly. You can also determine the pH from pOH as below:

pH + pOH = 14 pH = 14 - pOH

As the factor pOH is involved here, we need to discuss it in brief detail. Let’s go!

What Is pOH?

“pOH is the potential of hydroxide ions” Along with pH, you can also get an accurate value of the pOH in the solution with the help of our free pH and pOH calculator.

pOH formula:

pOH = -log([OH⁻])

OH⁻ Ions Formula:

Just like that of the pH, you can calculate the concentration of the OH- ions by rearranging the pOH formula as follows:

[OH-] = 10^-pOH

Ionization Constants:

Let’s talk about the ionization constants that could swiftly be determined with our best pH calculator. Generally, if the concentration of the hydrogen ions in the solution is increased, it becomes acidic and its pH goes below than 7. The same is for the pOH and bases. If the concentration of hydroxide ions is increased in a solution, the basicity increases and pH goes higher than the neutral that is 7. Okay, let us discuss the following reactions: Suppose we have a reaction of acid HA with water as follows:

HA ⇌ H⁺ + A⁻

For this reaction, we have the ionization constant for acid as:

Ka = [A⁻][H⁺]/[HA]

The same way we are going to have a reaction between a base and water as follows:

BOH ⇌ OH⁻ + B⁺

The ionoization constant for this reaction is as:

Kb = [OH⁻][B⁺]/[BOH]

Here the free pH calculator automatically goes for calculating Ka for acidic solution and Kb for basic solution. How does it sound?

How To Find pH From Ka?

Below is the formula to find pH from the dissociation constant Ka:

$$ a_1 = K_a \times \text{Concentration} a_2 = \sqrt{a_1} a_3 = \log(a_2) \text{pH} = -a_3 $$

The pH Scale:

Normally, the pH scale is designed to estimate the pH of any acidic or basic solution with the help of colours and pH values set corresponding to those colours. On a pH scale:

  • A pH of 7 indicates neutral nature of the solution
  • A pH of greater than 7 indicates that the solution is basic
  • A pH of less than 7 shows that the given solution is acidic enough

The overall pictorial chart of pH underneath will further vanish your doubts.

ph scale  

How To Calculate pH?

Let us go through a few examples to determine pH of a solution from various parameters given.

Example # 01:

How to find pH 0.25M solution of HCl?


We know that:

pH = −log[H+] pH = −log[0.25] pH = − (-0.602) pH = 0.602

Example # 02:

We have a 390ml solution of 8g of caustic soda. How to find pH from molarity?


Caustic soda is NaOH whose molecular mass is 40. You can also determine the molecular mass with the help of our molecular formula calculator. Anyways, let’s move forward:

No. of Moles = 0.2 (for calculations, click Mole Calculator) Now we have: Molarity = moles/volume

Molarity = 0.512 (for calculations, click Molarity Calculator)

At last we have:

pOH = -log([OH⁻])

pOH = -log([0.512])

pOH = -(-0.90) pOH = 0.90

At last we are going to determine the pH as follows:

pH = 14 - pOH pH = 14 - 0.90 pH = 13.1

How pH Calculator Works?

See how this free pH and pOH calculator goes for calculating the pH and pOH along with related elements.


  • From the first drop down list, do select which method you want to calculate pH with
  • After doing so, select the desired acid or base depending upon the selection you made
  • After that, go for entering all the parameters in their designated fields and select their units from their corresponding drop down lists
  • Now tap the calculate button


The free online pH solution calculator determines:

  • pH
  • pOH
  • [H⁺]
  • OH⁻
  • Pka:


What is the basic relationship among pH and pOH?

There exists an inverse relationship ampong pH and pOH. When pH increases, pOH decreases and vice versa. Moreover, the scale on which you are measuring the ion will decide whether or not it is acidic or basic in nature.

What is the relationship of pH and pOH with the Kw?

The value of Kw is exactly 1.0 x 10^-14. This value can be used to calculate pH and pOH. Also -logKw = 14 is the value that is when fed into the equation will give you pH and pOH depending upon the concentration you use. But the most efficient way to do so is commencing to our free pH calculator.

Why is the sum of pH and pOH 14?

As we know that both of these terms indicate the log of protons and hydroxide ions, respectively. The sum of pH and pOH is always 14. The reason behind the fact is that the product of hydroxide and proton concentrations must be equal to the equilibrium constant for the ionization of water, which is equal to 14.

What is the relation between pH and Kw?

As the Kw increases, pH also increases. That is why we can say there is a direct relationship among both of these parameters.

How does morality change with pH?

An increase in the molarity of a solution causes a considerable decrease in its pH that could be noticed by using a pH calculator from molarity.

What is the pOH of a solution at \(25^\text{o}\)?

The pH of any aqueous solution at \(25^\text{o}\) is always 14.

What is the difference between p and pH?

pH goes for indicating the acidic or alkaline nature of a solution with respect to a logarithmic scale. Whereas, the subscript p in the pH represents the negative logarithm of hydrogen ions.

What is the pH of blood?

The pH of blood is almost between 7.35-7.45 that you can also determine with the help of this free pH calculator.

What is the pH and pOH of pure water?

The pH and pOH of the pure water is always 7 (neutral).


Both pH and pOH are the quantities that affect the chemical conditions of the solution. In this read, we have discussed keenly the proper difference between both of these terms with suitable examples. Moreover, it has been also enlightened that these chemical parameters could be determined in seconds with the help of our best pH calculator. We hope that this article will help you a lot when you are going to perform a certain experiment in the laboratory.


From the source of wikipedia: pH, pH indicatorsCX, pOH, Extremes of pH, Applications, pH in nature, Calculations of pH

From the source of khan academy: Autoionization of water, Arrhenius, Brønsted–Lowry, buffers

From the source of lumen learning:  pH and pOH, ENVIRONMENTAL SCIENCE

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