One 90 mg Coffee Needs 2.5 to 6.8 Hours Before Bed to Drop Under 50 mg. Your Half-Life Decides Which
Caffeine's half-life ranges from 1.5 to 9.5 hours between healthy adults, per the Institute of Medicine. We ran one filter coffee and a double through the half-life math at 3, 4, 5, 6 and 8 hours to see how far back your cutoff really needs to be.