100 lumins / sq ft is pretty high. (30 lumens / sq ft is industrial standard) Depends on the activity in the garage. Detailed work = more light needed. My garage is 30X40 and I have 8 T8 2 bulb fixtures (about 3K lumens per bulb) so I have 48000 in 1200 sq ft = 40 lumens / sq ft. Pretty good...