Initial volume
Dilutant volume
Final volume
Dilution Factors
Total to stock
Dilutant to stock

Dilution Factor Calculator

By Jack Bowater
Last updated: Mar 25, 2020

You will find this dilution factor calculator useful if you have ever performed a dilution; from chemical experiments and the preparation of medicine, to making the perfect cup of coffee! As you've almost certainly used the dilution factor formula before, we have written this article to help you learn what is a dilution factor and how to calculate the dilution factor of any dilution you prepare. So, read on, so you no longer need to wonder how to find the dilution factor!

What is dilution factor?

The dilution factor (or dilution ratio) is the notation used to express how much of the original stock solution is present in the total solution, after dilution. It often given as a ratio, but can also be given as an exponent, however, this calculator will only show it as a ratio. Regardless if dilution factor is a ratio or exponent, it has two forms, either describing the parts of the stock solution to the parts of the dilutant added (S:D) or the parts of the stock solution to the parts of the total solution (S:T).

As the difference between these two representations is very slight, an example would help to make sure that you don't get the wrong answers and mess up your experiment! Let's say you have a 10 cm3 aqueous solution of acyl chloride. However, this is too concentrated for your experiment, so you add 90 cm3 of water to further dilute the solution. You end up with 100 cm3 of acyl chloride. As you have 10 parts of the stock solution, and 90 parts of the dilutant, the S:D ratio is 1:9 (canceling down from 10:90). In the S:T notation the dilution factor is 1:10, you have 10 cm3 of the stock solution that now makes up a 100 cm3 solution.

It is also worth noting that dilution factors only represent a loss of concentration - no molecules themselves are lost, just the number of them per mL decreases. This can be useful is several experimental situations. Although dilution factor is just a handy way of thinking about dilutions, dilutions are very common, both in science and in your day to day life. If you've ever made gravy, you've done a dilution. Ever washed your hands with soap? You've done a dilution. They are also useful in the lab. If you wanted to replicate experiments over a range of decreasing concentrations, you would prepare what is known as a serial dilution. They're also used in practically every chemical, and most biological, experiments, as the stock solution of your chemical is often far more concentrated than you desire.

Dilution factor formula

Now that we've discussed what is dilution factor, let's get down to brass tacks and talk about the dilution factor formula. But first, a brief section on how to represent the dilution factor. As we mentioned above, dilution factor is often expressed as a ratio. The simplest formula for both types or dilution factor are as follows:

  • S:D = stock volume:dilutant volume
  • S:T = stock volume:total volume

If these volumes are expressed in the same units, you can cancel each side down using their greatest common factor, you will end up with the simplest integer expression of the dilution factor. Some of you, however, may wish to express this ratio in the form 1:X, where X = how many parts of the dilutant/total solution there are for one part of the stock solution. This may leave you with some funny (not haha funny, but oh no funny) ratios, but their formulas are:

  • S:D = 1:(stock volume/dilutant volume)
  • S:T = 1:(stock volume/total volume)

Due to the limitations in current technology, this is also how our calculator expresses your results. We hope you can forgive us of making you do extra work.You may also see dilution factor expressed as an exponent, such as 3-1, 5-3 or 10-4. Now, do not be frightened by this new form! The exponent merely represents the ratio of the parts of the dilutant/total to the parts of the stock. Use the order of the ratio above:

  • S:D = exponent:1
  • S:T = exponent:1

Now, you may or may not know, that a number with a negative exponent is the same as putting that number as the denominator when the numerator is 1, and removing the negative sign. Our exponent calculator can help you with understanding this further, but for now, lets go through those examples we set out above:

  • 3-1 - 1/31:1 - 1/3:1 - 1:3
  • 5-3 - 1/53:1 - 1/125:1 - 1:125
  • 10-4 - 1/104:1 - 1/10000:1 - 1:10000

How to calculate dilution factor

If you're still asking yourself "how to find dilution factor?", then, we hope this section will answer all of your questions. So, just follow the steps below if you are want to calculate dilution factor by hand:

  1. Find any two of the following three values: volume of the stock solution (stock), volume of the dilutant (dilutant), and total volume of the solution (total). This can either be done theoretically (before your experiment) or experimentally (after your experiment).
  2. Use the two volumes to find the third. Use this equation: stock + dilutant = total. If you know which notation you would prefer to use (S:D or S:T), then you may not need this step, but we shall include it for completeness.
  3. Convert the numbers so that they are all in the same units.
  4. Decide which notation you require:
    • S:D = set the values of the stock and dilutant amount as a ratio - stock:dilutant
    • S:T = set the values of the stock and total amount as a ration - stock:total
  5. If required, cancel down the fractions by finding the Greatest Common Factor.

We have already provided an example in the What is dilution factor?, so, please check that section if you are still wondering how to find dilution factor. We will, however, tell you how to calculate the volumes you need from the dilution factor:

  1. Choose your desired dilution factor, its notation (S:D or S:T) and one of the variables either side of the colon.
  2. Divide the number after the colon (D or T) by the number before the colon (S). We will name this value will be known as the factor.
  3. Use the following equations depending on your choice of notation:
    • S:D = stock * factor = dilutant or dilutant / factor = stock
    • S:T = stock * factor = total or total / factor = stock

There you have it - we hope this solves any of your issues regarding dilution factors. You can always check your results with our dilution factor calculator, or just use it in the first place. It works in either to find the dilution factor or to find the volume required to achieve a certain dilution factor, just input the fields you know into our tool!

Jack Bowater
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