Here is how to do a draw-down chart:

Get some graph paper [or get one up on your puter]. In the middle of the paper [horizontal perspective] draw a 'mean' line across the page in the middle. Mark on the top of page 12 points [dots] across it evenly spaced representing months. Name the months above the dots.

The mean line represents $0 result which might be for a starting $5000 bank for instance. Each printed graph line above or below the drawn 'mean' line represents a unit of value depending on your average bet size, the horizontal graph lines might represent $10,20.50.100 etc.

At the end of the first month if you are in say $500 profit and your horizontal graph lines represent say $20, count up 25 lines and on the vertical line that represents the first month mark with a dot. Draw a line from that dot back to the start of your 'mean' line. Keep doing that, joining the dots every month [can do one for weeks if you like]. After 12 months the lowest point reached below the 'mean' line is your max. draw-down for 12 months.

The above is for a profit and loss draw-down chart. Naturally you can do them to represent almost anything [how many pots you drink a month even].

Just change the values involved to suit your needs. It might be a SR draw-down chart for instance which will let you know SR max-drawdown [max run of outs] in 12 months. Just give everything values and away you go !!