When you have a small amount to weigh out, don’t worry about being exact. Instead, it’s easier to change the volume to match what you weigh to get your desired concentration.
If you start with a desired weight/volume concentration, divide your actual measured weight by that desired concentration. Taking any unit conversions into account, the weights cancel out, leaving you with volume
If you start with molarity, just add a step to convert to weight/volume by multiplying the molarity by the molecular weight.
It can also be helpful to do the weighing in the tube so you don’t have to worry about loss during transfer.
Hope that helps!
more on metric conversions: blog: bit.ly/metric_calcs ; KZfaq: • Metric conversions & s...   
 
more on sig figs (which I ignored in this video) here: bit.ly/significantfiguress & • Figuring out sig figs ...   
  
more on dimensional analysis: bit.ly/dimensionalanalysising & • Dimensional analysis (...   
  
more about concentrations: bit.ly/sciencestocksolutions ; KZfaq: • Concentration - ways t... & • Working with relative ...    
  
and a couple cheat sheets for molecular weights: drive.google.com/file/d/1TqCR...    
  
and concentrations: drive.google.com/file/d/1v7pf...     
 
more lab-mathy things: thebumblingbiochemist.com/let... & kzfaq.info?list...
 
more about all sorts of things: #365DaysOfScience All (with topics listed) 👉 bit.ly/2OllAB0 or search blog: thebumblingbiochemist.com