If you find it difficult to use this page, ask your doctor or your asthma nurse to tell you what your normal predicted Peak Flow is. Choose the red curved line which shows what your Peak Flow should be for your sex and height.
Height is given in both inches and centimetres.
Imagine a straight line vertically from your age at the bottom of the chart. Where your vertical line crosses your red curve, imagine a horizontal line. The horizontal line will cross the left axis at the predicted notmal figure for your Peak Flow. There is a lot of variation between normal people. Here is an example of how to use the chart.