Formula needed

[JMBullfrog]

I bought myself a 30 litre stainless steel brewing vat for Christmas. It is a nice rig with a cone-shaped bottom and two taps - one above the other. I just use Cooper's brew packs because I live in Carnarvon 1000 kms from Perth. The recipes for these call for making 23litres. Using 30 litres of water seems to dilute the finished taste and alcohol content. Does anyone know the formula to calculate the extra sugar needed to bump the alcohol content up to say 5%?

 

[Mayor of Mildura]

Coopers kit + 2kg sugar in a 30L batch is 5.3% according to beersmith.

 

[JMBullfrog]

Coopers kit + 2kg sugar in a 30L batch is 5.3% according to beersmith.

Thanks for that. So I probably would be in the ball park with the load I used.