1lb batches. this gives me lots of soap to test new fragrances/oils with without sacrificing too much if things go bad. also a great way to test 1oz fragrances, no measuring needed and it's cheap
I'm primarily a hobbyist so generally 800 grams which fits an 8 inch silicone loaf mold like the kind sold by BB, WSP and Bebe (Richard). If I'm making soap for a swap or an event of some sort, I'll double or triple it. The most I make at one time is 5 lbs.
I have 2 log molds. Each one makes 4 pounds of soap. I usually only make 1 at a time but when I make a double batch (using both molds) then I have 8 pounds of soap.
Like judymoody, I'm a hobby soaper, so I keep my batches on the small side. My normal size batch is 2.5 lbs (just over 1 kg), and for my experimental 'test' batches I do 1.2 lbs (.54 kg). The most I ever make at a time is 5 lbs (2.26 kg), usually around September to prepare for Christmas-time gift giving.