What is “lab math”?

Lab math is basic math/algebra that is used in making solutions and adjusting concentrations for experiments in a wet lab.

Why does lab math matter?

When joining a lab as an undergraduate, graduate student or research assistant, there can be a steep learning curve for a lot of skills. Not only are you learning how to do experiments and think like a scientist, you also learn all of the chores that have to be done for a wet lab to run efficiently. Every lab runs in a slightly different fashion, but they all must keep things clean, organized and well stocked with reagents and solutions to have the ability to run experiments. Lab math comes into play when considering solutions. Some solutions are used by the whole lab so they are made in bulk while others are made in small batches for specific reasons. Therefore, anytime you want to do an experiment, lab math will be involved in some way. Learning lab math skills will allow you to be an active lab member and give you the ability to try any experiment you want! Hence, lab math can really help build your confidence as an independent experimenter.

Lab math tips and tricks

There are a lot of great free websites to explore the different kinds of lab math you might encounter. As an example, here is a website that clearly explains how to solve lab math problems: https://bitesizebio.com/11120/a-guide-for-solving-your-lab-math-problems/

For a life sciences wet lab, there are a few common equations used in many aspects of solution-making. Listed below are common equations with tips on when they are used to help you get started:

A common liquid dilution equation is (Concentration1)(Volume1) = (Concentration2)(Volume2) or C1V1=C2V2

When: This equation is often used when you have a stock liquid solution and need it at a different concentration. For example, if you have 100% ethanol and want to make 75% ethanol.

TIP: make sure you calculate how much solution you will need before you start.

TIP: if it is easier, think of this in ratios.

weight/volume calculations

When: Weight/volume calculations are done when you are adding a dry reagent to a liquid volume in a certain percentage. For example, if you need to make a 2% agarose gel (where the agarose is dry and added to a liquid buffer).

TIP: for weight/volume calculations remember that a 1% solution = 1 g in 100mL of solution

Molarity!! Think back to high school when you learned about the molecular weight of a chemical.

When: Molarity calculations are used when you need a specific molarity of a chemical in a solution. For example, making a 2 mM solution of NaCl.

TIP: 1 Molar = molecular weight in grams in 1 Liter of solution.

TIP: 1 Molar = 1000 milliMolar

X solutions. Often labs make more concentrated stocks of solutions so that they can be diluted down when using them.

When: 10X or 20X stocks of common solutions in lab are often made to help keep the lab stocked. For example, a 10X stock of phosphate-buffered saline (PBS) contains 10 times the concentration of all solutes relative to the working stock, or stock used in the actual experiment. Also, stock solutions make it easier to add a smaller volume of a solution. For example, often loading dyes that are added to samples when loading gels are in a stock, like 6X, so that you can add a little bit of loading dye to your sample to make it be at 1X.

TIP: Use C1V1=C2V2 (#1 above) to convert stock solutions to working stock concentrations.

How to build your lab math confidence

Like a lot of things in life, practice makes lab math easier. The more you practice in everyday situations, the more confidence you will gain. However, this can be really intimidating when you first start. Here are a few tips to help you along:

Ask a lot of questions! When you are learning how to do things around lab, ask others how they figured out making a certain reagent. Hearing how someone else solved a lab math problem will help you see how things are done.

Write down all of your math in your lab notebook every time you do it. Visually seeing the math can help solidify it in your mind. This also has the added bonus of tracking your math. If something goes wrong (which happens sometimes, it is ok!), you can go back and figure out what happened and learn from your mistake.

Take your time. Lab math is not something to rush. Take your time to think it through so the next time you come across the problem it will be easier to figure out. Even better, write out your lab math before you need it so you do not feel rushed in the moment.

It is ok to use a calculator! If it makes you more comfortable to use a calculator when doing simple math, then use it.

Create a cheat sheet to store in your lab notebook. When experiments get busy, it is easy to forget some of the basics. If you make a little cheat sheet of the common conversations you use and leave it in the front or back of your lab notebook, then you can refer to it when you draw a blank.

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