Hi! I'm not sure if this helps, but I found a conversion listed in another forum.

http://www.proteacher.net/discussions/showthread.php?t=3094

Just substitute in your percentile into the formula where they have .86 you would put .99. I got it to return a value of 137. My son's were given as percentiles too and I had to dig up the way to calculate a few months ago. smile