Should I Top Off Fermenter with Water?

I brewed two batches of extract beer (stout and hefeweizen), following the kit recipe each time. Each kit was for a 5-gallon batch. The instructions were (summarizing):

• Put 3.5 gallons of water in the primary
• Boil 2 cans of extract with 2 gallons of water for 60 minutes
• Add boiled wort to water in primary

For the stout, target OG was 1.040-1.042 and I got 1.048. Target FG was 1.012-1.014 and I got 1.016.

For the hefeweizen, target OG was 1.042-1.044 and I got 1.044. Target FG was 1.008-1.012 and I got 1.013.

Both batches came up short of 5 gallons in the fermenter.

After fermenting and racking to the bottling bucket, I had 4.75 gallons of hefeweizen and 4.5 gallons of stout.

Should I have added more water to the primary at brew time to hit the OG range specified by the kit? To make a total of 5 gallons in the primary? To make a total of 5.5 gallons in the primary? Or just let it go as I did?

(Because my OGs were close to the specified ranges, I figured it was good enough and let it go.)

top off to 5g in the fermenter when first brewed. don't worry about amounts after that

Most recipes are set up for 5 gallon batch. Your recipe has you using 5.5 gallons of water, so it's likely expecting half a gallon to boil off and be otherwise lost. You may, however, be losing more than that.

So go for 5 gallons in the primary.

Thanks, all. I kept a pretty strong boil going for the 60 minutes both times, so I must have boiled off more liquid than the recipe assumed. Next time, I will add enough water in the primary to hit the target volume (5 gallons, for the batches I mentioned).