Reconstitution Calculator

Created by Komal Rafay
Reviewed by Dominik Czernia, PhD candidate and Jack Bowater
Last updated: Sep 24, 2022

Have you found yourself in a situation where you need to prepare a solution from a powder and require the assistance of a reconstitution calculator? Or maybe you need to reconstitute and administer a drug? These are both examples of how to calculate reconstitution.

Whichever reason brought you to us, you can relax because you will find answers to all your questions and more, including the reconstitution formula and the process of calculating the reconstitution of medication.

Reconstitution calculator

The reconstitution calculator is a simple and easy-to-use tool that allows you to determine the reconstitution concentration of a solution that you may have to produce using a dry ingredient and a diluent.

The calculator requires you to input:

  • The mass of the dry ingredient, which in the case of medicine, is given on the vial; and
  • The volume of the diluent which you are using to make a solution of a certain reconstitution concentration.

What's more, you can use our tool to find any of the three values as long as you input the other two. This can come in handy, especially in the reconstitution of drugs and various medications where having these values as accurate as possible is crucial.

Reconstitution is not limited to medications only, as you can also find this phenomenon used daily. For example, say on a Sunday morning, you decide to have pancakes as your breakfast feast, and you grab the dry mix from the pantry. All you have to do is add the liquid ingredients (milk, eggs, or oil) to start making the pancakes. This is how we use reconstitution in our daily lives without sometimes even realizing it!

Now, the next time you find yourself in a situation where you have to mix a dry ingredient with another liquid to obtain your desired solution, you can surely rely on our reconstitution calculator to help you get all the weight and measurements correct.

💡While we are on the subject, do check out our solution dilution calculator, which will help you learn how to dilute a stock solution of known concentration.

What is reconstitution?

You might have tried making jello at home, right? It is a simply balanced ratio of the instant mix powder from a pouch and cold and hot water. This mixing of water with the gelatin powder to obtain jello is a convenient way to describe the process of reconstitution.

We define reconstitution as:

the process of adding a liquid (diluent) to a dry ingredient to obtain a specific concentration of the resultant solution.

The dry ingredient can be in any weight measurement: micrograms, milligrams, or grams, and similarly, the wet part, or the diluent, is in any volume measurement: microliters, milliliters, or cubic centimeters. It makes the unit of reconstitution concentration a ratio of mass and volume, usually in mg/ml.

Reconstitution can sometimes also mean reinstating an object or ingredient to its original or usable state. For instance, you might have heard someone ask how to reconstitute honey or dried mushrooms. In the case of honey, to get rid of any crystallization, you can place it in a warm place or just pop it in the microwave for a few seconds. For mushrooms, you need to soak them in water for some time.

We have a volume conversion tool that helps convert between various units of volume.

The reconstitution formula derivation

When doctors prescribe a drug, they usually specify its concentration, and the medicine itself comes in pre-packaged vials. So, all that is left to do is to add the correct amount of diluent. That is what the base formula is for figuring out the volume of the diluent:

dose volume = dose / reconstitution concentration


  • dose - The mass of the powdered or crystalline drug; and
  • dose volume - The quantity of diluent you need to add to the powder or crystalline drug.

By rearranging the above equation, you get the formula for reconstitution concentration:

reconstitution concentration = dose / dose volume

This is the formula we use as the base for our calculator, and you can quickly determine any of the three values, as long as you don't forget to input the other two accurately.

You might find our alligation calculator a handy tool to determine solution concentrations based on the allegation ratio.

How to calculate reconstitution?

The reconstitution calculator is a handy tool for all who need to prepare a solution using a dry ingredient and a diluent.

Our tool is straightforward to use:

  1. Input the dosage, which is the mass of the dry ingredient. In the case of medications, they come in vials, and you can find the dosage on the label.

  2. Input the required or prescribed amount of the diluent, which in case of medication is also on the drug's vial or is advised by the doctor.

  3. All left for the calculator is to determine the reconstitution concentration in mg/ml. This value is the concentration of the resultant solution that you obtain from mixing the dry and wet ingredients.

Still, let's say you find yourself in a situation where you cannot use the tool. For instance, in a classroom, your teacher decides to conduct a surprise quiz, and one of the questions is "How to calculate reconstitution?" To answer it, you can follow the steps below:

  1. Note down the mass of the dry ingredient.
  2. Note down the volume of the diluent.
  3. Divide the mass by volume.
  4. The result is reconstitution concentration.

Calculating reconstitution of medication

The preparation and administration of drugs is an essential process for doctors, nurses, healthcare practitioners, and caregivers.

The fundamental thing to do is to study the label or leaflet of the medicine or vial, which comes with instructions, including:

  • Contents of the vial;
  • Mass of medicine in the vial;
  • Desired volume of the diluent for optimum concentration;
  • Reconstitution concentration;
  • Expiration date before and after reconstitution; and
  • Optimum storage temperature before and after reconstitution.

The dosage of the medication needs to be precise, and hence, reconstitution cannot be taken lightly. Usually, not all medications are in the form of tablets or syrups. Healthcare staff need to prepare them as a solution using the drug in powder or crystalline form with the liquid, which acts as a diluent or solvent.

Remember, the reason to keep certain medications in a dry form is to increase their storage life. Once you reconstitute them, you should use them within their new shelf-life.


Is reconstitution different than dilution?

Yes, both terms are different. Reconstitution is the process of adding a liquid diluent to a dry ingredient to make a solution. In dilution, we add more solvent to a solution of a higher concentration to reduce its concentration.

For instance, if you make lemonade with too much sugar, you can add water to reach the desired flavor. This is dilution. But, in making pancakes, you can not add diluents to your liking because the batter needs to have the proper consistency. The appropriate ratio of wet and dry ingredients is reconstitution.

How do I reconstitute medication dosage?

The reconstitution of medicine doses has to be accurate and the process involves:

  1. Mass of dry ingredient.

  2. Volume of diluent .

  3. Reconstitution concentration. The reconstitution formula is:

    Reconstitution concentration = mass of ingredient / volume of diluent

  4. You can rearrange the formula to calculate the required amount if you know any two variables.

How do I obtain 250 mg/ml reconstitution concentration from 500 mg of ceftobiprole?

You need 2 ml of diluent to reconstitute 500 mg of ceftobiprole to get a reconstitution concentration of 250 mg/ml. You can find it using the below formula:

diluent volume = ceftobiprole mass / reconstitution concentration

How do I find reconstitution concentration for 350 mg of Vancomycin?

You obtain 70 mg/ml of the reconstitution concentration, assuming you dilute 350 mg of Vancomycin, with 5 ml of sterile water.
In the reconstitution concentration formula, you need to divide the mass of the medication by the volume of diluent to find the result.

Komal Rafay
Dose volume
Reconstitution concentration
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