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Rate Constant Calculator

Rate Constant Calculator

Put the values & determine the rate of change along with the rate of reaction in dynamic processes.

Elementary step:

rate = K[A]2

rate = K [A]2[B]2

rate = K [A]2[B]2[C]2

Order Of Reaction (Molecule A)

Concentration [A]


Half life T1/2


Order Of Reaction (Molecule B)

Concentration [B]


Half life T1/2


Order Of Reaction (Molecule C)

Concentration [C]


Half life T1/2



Table of Content

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Employ the rate constant calculator to calculate the rate and concentration of the given substance over a specified period of time. This calculator makes it easy for you to find the constant rate and reaction rate.

Rate Constant & Reaction Rate:

Rate constant is known as the proportionality constant that shows the relation between the molar concentration of the reacting substance and the rate of reaction

Rate constant tells us how fast or slow a reaction is. It is affected by temperature and the activation energy. Higher temperature causes an increase in rate and lower temperature energy also causes an increase in rate constant.

The change in concentration of reactants and the products per unit of time is known as reaction rate. It is the quantification of how quickly a reaction takes place

This reaction rate can be affected by different factors including concentration, temperature, presence of a catalyst, and the surface area of a reactant.


kt = [R0] – [R]

k = ( [R0] – [R] ) / t

k = Rate constant.
[R0] = Initial concentration of the reactant (when t = 0)
[R] = Concentration of the reactant at time ‘t’

How To Calculate The Rate Constant?


Suppose the initial concentration of A ([A0]) is 0.2 M, and after 30 minutes, the concentration ([A]) has decreased to 0.1 M. We want to calculate the rate constant (k) for this reaction.


As by the laws of the rate constant in this case the 1st order rate equation can apply.

[A] = [A]0 . e^-kt

Given Values:

  • [A] = 0.1M
  • [A]0 = 0.2 M
  • t = 30 minute

Step # 1:

Substitute these values into the equation and solve for k

0.1 = 0.2 ⋅ e ^−k⋅30

Step # 2:

Divide both sides by 0.2

e ^−k⋅30 = 0.5

Step # 3:

Take the natural logarithm on both sides

−k ⋅ 30 = ln (0.5)

Step # 4:

Solve for k

k = − 30 / ln(0.5)

Calculate the numerical value for k and you’ll get the rate constant for this first-order reaction.

Laws of Rate Constant:

The rate of reaction calculator offers rate of reaction formulas for Zero Order, First Order, and Second Order reactions.

Zero Order:

The rate of the reaction is independent of the concentration of the reactant is known as the zeroth-order reaction. In this law, the k remains constant regardless of the change in concentration.

Half-life = A / (2 × k)

Rate Constant

1st Order:

In this order, the rate of reaction is directly proportional to the concentration of the reactant. In this, the reaction rate increases with the increase in reactant concentration.

Half-life = 0.693 / k

Rate of the reaction = k × A

1st order of Rate Constant

2nd Order:

The rate is directly proportional to the square of the concentration of one reactant or the product of the concentration of two reactants. In this, the rate increases with the change in reactant concentrations.

Half-life = 1 / (k × A)

One substance: Rate of the reaction = k × A × A

Two substances: Rate of the reaction = k × A

2nd Order of Rate Constant


What is Half-life T1/2?

Half-life T1/2 refers to the time that is taken for a substance to decrease by half. In radioactive decay, it is the time for half of a radioactive substance to decay into a more stable form. Different drugs have different half-lives and it takes 5 x to be considered cleared.

What Is The Unit Of Rate Constant?

Unit of rate constant k = Unit of rate constant (k) = L mol -1 s. -1.

What Is The Relation Between Temperature & Rate Constant?

If the temperature goes high then the rate constant decreases and if the temperature decreases the rate constant decreases.

Can The Rate Constant “K” Be Negative?

No, the rate constant can’t be negative because it quantifies the pace of concentration change over time.