The average molecular speed can be calculated from the Maxwell speed distribution
as 
  
    
      
        
          v
          
            
              a
              v
              g
            
          
        
        =
        
          
            8
            
              /
            
            3
            π
          
        
         
        
          v
          
            
              r
              m
              s
            
          
        
        ≈
        0.921
         
        
          v
          
            
              r
              m
              s
            
          
        
      
    
    {\textstyle v_{\rm {avg}}={\sqrt {8/3\pi }}\ v_{\rm {rms}}\approx 0.921\ v_{\rm {rms}}}
   (or, equivalently, 
  
    
      
        
          v
          
            
              r
              m
              s
            
          
        
        =
        
          
            3
            π
            
              /
            
            8
          
        
         
        
          v
          
            
              a
              v
              g
            
          
        
        ≈
        1.085
         
        
          v
          
            
              a
              v
              g
            
          
        
      
    
    {\textstyle v_{\rm {rms}}={\sqrt {3\pi /8}}\ v_{\rm {avg}}\approx 1.085\ v_{\rm {avg}}}
  ).
{\displaystyle \Phi _{N}={\frac {\Delta PAN_{A}}{\sqrt {2\pi MRT}}}.}