Flow velocity for fixed diameter in pipes under pressure

The app returns the flow rate in pipeline according to a fixed flow velocity
Pipe section
Flow rate

Nominal diameterdn(mm)
Thicknessen(mm)
Internal diameterDi(mm)
    
Area (mm2)
  (m2)
   MinMax
Speedv(m/sec)
Flow rateQ(m3/sec)
  (m3/h)
  (l/min)