Boil off.

One thing I have found that I can not get consistent is the amount of Boil off (amount of water boiled away during the boil).

Is there a way to determine this during the boil?

My thinking:

1) check liquid levels during boil. (How)
2) temperature of the boil (does it vary)
3) amount of rolling boil (hard to get right)

Don't say a mark on the propane dial I tried that and it did not work, the flame power seems to change as the tank empties.

Any other suggestions.

I use a dip stick made of wood. Pour in a gallon of water in your pot, put in your dip stick, where the water level is, carve a mark on your stick. Repeat this process until you get well above your normal volumes. Then when you want to know what your volumes are during the boil, just use the dip stick. I usually turn the heat down a bit so the boil isn't nearly as violent making it difficult to tell where the wort really is on the stick.

Look up brew in a bag website ad dowload their spreadsheet. They have built in a calculation based on your kettle diameter. I use this aling with a ss ruler to get precise measurements any time