How do I figure out my boil off rate?

I bought a 30liter (7.9 gal) Euro tank from Austin Homebrew Supply. Here is the link:
Austin Homebrew Supply

Hers the specs from the website:
Specifications:

Capacity: 31.7 qt (7.9 gallons or 30 L)
Diameter: 15 in (38.1 cm)
Depth: 13 in (7.62 cm)

It will fit across 2 burners on my stove and I am curious on how to figure out the boil off rate. I has a lot of surface area and I think will evaporate much quicker then a narrow pot. I just started All grains and the way I see it I might have to drain an extra 1/2 to 1 gallon to achive an hour boil and hit my target volume.

Will Beersmith or promash help with this? Will boiling water give me an approixmation?

 

Boiling water will give a very good approximation.

 

Depends on your day and altitude etc. It is not an exact science, but after a few time you should get to know your equipment.

I was told a gallon an hour is a good start.

- WW

 

Yeah, I think that's a good ballpark figure to start with. My boil-off rate is around five litres per hour, which is (I think) a little over a gallon per hour.

 

yeah, just start with about a gallon, that about what I get. After you get some more experience it will be second nature to factoring boil off.

 

To figure out your boil off rate just put a measured amount of water in your pot then boil for an hour. Then measure how much water is left. Be sure to make your measurements at the same temperature because water expands as it gets hot.

 

That is good info. I'll start with that. I'll put 7 gallons in a boil for an hour. I will post my findings in here in case someone else wants to get the same pot.

 

just remember that different boil intensities will change the rate. So it's best to keep it as constant as possible between brews.