How to figure out boil off on first time brew

Im brewing my first batch this saturday of an extract honey wheat and I would like to do a full boil but Im not sure how to acomplish this and through my searches I havnt been able to find an answer.

Beer smith tells me based on my equipment (a 10 gallon Megapot) with a weight of 19 lbs that to obtain a 5 gallon brew I will need 5.7 gallons as the volume of water. With 8.8% evaporation rate, cooling shrinkage of 4%. and and cooling loss of .21 gallons

Does this sound accurate? Also when it says 5.7 gallons is that before or after I add my DME? Is there a more accurate way of figuring this out if you dont have any brews in the past?

Sounds about right. You won't really the specifics of your own setup until you get a few brews under your belt.

I usually get about 1.5 gallons of boiloff during my full boils (5 gallon batches).

Last brew I did, I started with 5.5 gallons, wound up with 4 gallons

I usually lose about a gallon for 60 minute boils. I think if you started with 5.7 gallons you may come up short of 5. But like stated above, without actually doing some batches with your equipment you will never know. Can guess all you want but doing it is what you need to do. Start with the 5.7 and if you come up below 5 then you know how to adjust for the next batch.

My keggle boils off about 1 gallon per hour...I think 8% is a bit shy....are you brewing outdoors or in?

So, I too am making the transition to full boil. If I was to come up short of 5 gallons after boil, would I still need to top off to get to 5 in my primary? Or am I just gonna have less beer?

helibrewer said:

My keggle boils off about 1 gallon per hour...I think 8% is a bit shy....are you brewing outdoors or in?

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It will be indoors on gas stovetop 2 burners

I did a test run boiling water for half an hour (or so) to get an idea of the boil-off rate before I brewed. It's not necessarily exactly the same, but it should be close.

Be careful, also, because there's really not a good reason to expect that boil-off will be a % per hour---more likely it's a fixed rate of gallons per hour (assuming you maintain a consistent boil). So if you do differently sized boils, you may need to adjust the % rate to give you the right absolute rate. (That is, if you get to that level of precision....)

First off, measure out pre-determined volumes and mark your kettle...or calibrate your mash paddle in 1/2 gallon increments. At the end of your hour, check your volume and the gravity (corrected for temp). Adjust your volume with additional water if necessary to achieve your post boil OG. Make a note and start with that much more water next batch.

Boil off is usually lower indoors because the humidity is usually higher indoors than out....Except in the summer east of Colorado

Ok cool some good advise here Thx. I with mark my mixing spoon and do an hour long boil of just water and use that for my basis then on brew day I will check the gravity and be able to adjust it even closer.. Thx for the tips all

Too many variables, On my gas stove I would boil off about 1/2 gallon/hour now with my turkey burner I am over 1 gallon an hour.
Since I am working in a non temperature controlled environment I would expect my boil off rate to change depending on the weather.

I would assume 1.5 gallons of boil off if you are doing a full boil. Chances are your going to be between 1-1.5g per 60 minutes, assume 1.5g. You will probably lose .15-.25gal to trub, worst case you end up with 5 to 5.25 gallons of beer. You can always boil off extra water with another 15-20 mins of boil if you over estimate, or just take the extra beer if your gravity is fine.