Choose Bin Sizes for Histograms in Easy Steps + Sturge's ... Step 3: Decide how many bins you need using your best guess and using the guidelines listed in the intro paragraph above. Step 4: Divide your range (the numbers in your data set) by the bin size you chose in Step 3. For example, if you have numbers that range from 0 to 50, and you chose 5 bins, your bin size is 50/5=10.