Lab books will often include reagent tables which provide a clear overview for the required quantities of chemicals. When working in the labs using scripted procedures, you will usually encounter some missing values in the provided tables, and you will need to calculate these missing values as part of your preparations. The video below gives a guide to some of the common calculations which may be required.

Even with a completed reagent table, it is common practice to then append an 'Amount taken' row to the table, and record the actual masses used in the lab. These are likely to differ, especially with masses, as it is unlikely you will weigh out the precise amount calculated. It is also good practice to record the quantities directly in the units used to measure in the lab, even if your calculations are in a different unit. Mistakes do happen with converting between units, and recording what you actually did (and at the time you did this) may prove crucial in uncovering your mistakes. For instance if you wanted to weigh 50 mg in the lab, and your balance is in grams you should record the exact mass and units you weighed out on the balance (with all decimals), e.g. 0.0494 g. For volumes it is common to record the mode (eg 25 mL measuring cylinder or 2 mL syringe) which provides an idea of the accuracy used. Some people may additionally add a 'Source' row to their table, and record the manufacturer or other details of the chemicals used.