How late in the day can you drink coffee?

Short answer

One cup of coffee is safe up to about 9 hours before bed. If you sleep at 11 p.m., that's around 2 p.m. A high-caffeine pre-workout needs 13 hours, so before about 10 a.m., to protect your sleep.

How late in the day can you drink coffee?
'Coffee at lunch is fine, coffee at dinner isn't' — is that true?
Everyone says to cut coffee after a certain hour, but no one agrees on the hour. We looked at studies that changed when and how much caffeine people took, then measured their sleep.
Caffeine really does cut sleep
956 people: about 35 minutes less
An analysis that pooled 22 trials with 956 people found that on caffeine days, sleep dropped by 34.67 minutes on average and the share of deep sleep fell. Another analysis of 24 studies found 45 minutes less sleep and 9 more minutes to fall asleep.
It's not just an evening problem
Even 6 hours before bed, it disturbed sleep
In one study, people took 400 mg of caffeine, about three to four strong coffees, right at bedtime, 3 hours before, or 6 hours before. All three disturbed sleep compared with a dummy pill. Several strong coffees in the afternoon still reach your night.
So how early is early enough?
The bigger the dose, the earlier the cutoff
23 people took 100 mg (about one cup of coffee) or 400 mg at 12, 8 and 4 hours before bed. 100 mg made no difference to sleep, even at 4 hours. 400 mg at 4 hours cut sleep by 50.6 minutes, and even at 12 hours it cut deep sleep by 20.6 minutes.
But you can't feel it
Deep sleep dropped, yet people felt they slept fine
In the same study, when 400 mg was taken 8 or 12 hours before bed, measured deep sleep went down, but people's own rating of sleep quality didn't. Feeling like 'coffee never affects my sleep' isn't a reliable guide.
The cutoff times
One coffee: 8.8 hours. Pre-workout: 13.2 hours
An analysis of 24 studies calculated that to avoid losing sleep, one coffee (250 mL, 107 mg caffeine) should come at least 8.8 hours before bed, and one serving of pre-workout (217.5 mg) at least 13.2 hours before. For an 11 p.m. bedtime, that's 2:12 p.m. and 9:48 a.m.
Bottom line: one cup by 2 p.m., strong stuff in the morning
More caffeine means an earlier cutoff
400 mg of caffeine cut sleep even 6 hours before bed, and bigger doses lingered longer. If you sleep at 11 p.m., finishing one coffee by about 2 p.m. works, and several strong coffees or a pre-workout are best done in the morning.