Dilute a Stock Solution

Understanding Stock Solution Dilutions

What is a Stock Solution?

In chemistry and biology, a stock solution is a highly concentrated mixture of reagents. Laboratories use stock solutions to save space and reduce the time spent weighing out dry chemicals. When an experiment is ready to be performed, you simply dilute a small portion of the stock into a solvent to create your working solution.

How This Calculator Works

This stock dilution calculator automates the unit conversions and math required to figure out exactly how much of your concentrated stock you need to pipette into your final mixture. Simply enter your current stock concentration, your desired final concentration, and the total volume you want to end up with.

The Dilution Formula (C1V1 = C2V2)

The standard equation used to determine how much stock solution is needed is:

• C1: Concentration of your starting stock solution.
• V1: Volume of the stock solution you need to add (this is what the calculator solves for).
• C2: Desired concentration of your final working solution.
• V2: Total final volume of your working solution.

Step-by-step Example

Let's say you have a 100 mM stock of a chemical, but your experiment requires 50 mL of a 10 mM working solution. Here is how you calculate it manually:

1. Set up the equation: 100 mM × V1 = 10 mM × 50 mL
2. Solve for V1: V1 = (10 × 50) / 100
3. Result: V1 = 5 mL.

This means you would take 5 mL of your 100 mM stock and mix it with 45 mL of your solvent to reach your total volume of 50 mL.

Common Mistakes

• Forgetting to subtract: The V1 result is just the stock volume. Remember to subtract V1 from your final total volume (V2) to figure out how much solvent to add.
• Mismatched Units: A very common error is trying to calculate C1 in molarity while C2 is in millimolarity. Always convert to the same unit before doing the math (our calculator handles this for you automatically).