I usually get about 300, sometimes a bit higher , sometimes a bit lower....my fev1 is in the mid 40's. I love doing the peak flow ( have been using one for years) You can also use it after the vest or the flutter to help get things up. Its very effective. Sometimes i cant always tell if i am getting sick because i always have a cough. So i usually do my peak flow each day once or twice and know my "baseline numbers". When i am feeling like i am getting sick, i keep an eye on my peak flow numbers and they can be a good indication when its time for more aggressive action.