Diluting fermented wort

I bottled my first beer a couple of days ago and just boiled my second wort. I underestimated the amount of evaporation and ended up with a considerably smaller volume than expected.

Is it possible to dilute the wort after fermentation is done? Is there a maximum dilution percentage? I was thinking about diluting 3.6 liters to max 5 liters. That would increase the volume by almost 40 %.

If you plan on diluting your wort, you need to know the original gravity of what you boiled. If your boiled wort is at your predicted O.G., then I would suggest not diluting and just appreciate the smaller volume that you have. If, however, your O.G. is high, then you could dilute down to your predicted O.G. level.

I would dilute prior to fermentation, that tends to be the procedure when doing partial boils.

Is this a kit, partial boil, all-grain. More information might provide better responses than what I've given you.

This was an extract boil with some steeped crystal malt. Boil volume was 4 liters (really all my pot can safely handle. That was added to 2 liters already in the bucket.

I pitched the yeast, checked the scale on the side of the bucket, and it was at 3.6 liters. The hydrometer was broken so I have no OG. I have a predicted one from Beersmith, though.

If you just boiled off too much volume, then I'd say your good to add some water, but if you're going to do this after fermentation, then I'd pull a sample and then see if you really want to dilute it. Some of the best beer comes from making mistakes.

That's a very good point. I set out to make a different beer from my first one, without buying a lot of new ingredients, and this will definitely be different. Of course, it will also run out much faster.