The pressure is the scalar proportionality constant that relates the two normal vectors:

  
    
      
        d
        
          
            F
          
          
            n
          
        
        =
        −
        p
        
        d
        
          A
        
        =
        −
        p
        
        
          n
        
        
        d
        A
        .
The pressure due to a liquid in liquid columns of constant density or at a depth within a substance is represented by the following formula:

  
    
      
        p
        =
        ρ
        g
        h
        ,
      
    
    {\displaystyle p=\rho gh,}
  where:

p is liquid pressure,
g is gravity at the surface of overlaying material,
ρ is density of liquid,
h is height of liquid column or depth within a substance.Another way of saying the same formula is the following:

  
    
      
        p
        =
        
          weight density
        
        ×
        
          depth
        
        . {\displaystyle p={\text{weight density}}\times {\text{depth}}.}