If your ratio of lipofectamine (µl) /DNA (µg) works fine for your experiments, you should keep the same ratio for your transfection in the 6-well plate. In 6 well plate, I usually work at a DNA quantity of 1 µg but you can go further. I add lipofectamine depending on my transfection ratio (usually 3 µl for 1 µg of DNA) and I adjust the final volume to 2 ml.
Flore answer above is probably the most convenient way to extrapolate the recipe for transfection to different sizes of well. However, since lipofectamine transfection works in part by deposition of the liposomes onto the cells, the area occupied by the culture also has relevance. you can also
Flore answer above is probably the most convenient way to extrapolate the recipe for transfection to different sizes of well. However, since lipofectamine transfection works in part by deposition of the liposomes onto the cells, the area occupied by the culture also has relevance for reproducible results. In this link you will find a handy comparison of the growth area for different dishes and multiwells http://microbiology.ucdavis.edu/privalsky/tc-growth-area. Thus with the relation of areas 6well/96well=9.5/0.32=29.7, the factor you have to use to multiply the values in 96 well to translate them into 6 well.