Caffeine cutoff calculator

How much caffeine is still in your body at bedtime, and whether each drink was early enough.

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How it works

Your body clears caffeine at a fairly steady rate. Each half-life, half of what’s left is gone. The calculator adds up what’s left of every drink at your bedtime:

caffeine left = amount × 0.5 ^ (hours until bed ÷ half-life)

The average half-life in healthy adults is about 5 hours, but it ranges from 1.5 to 9.5 hours between people [1]. Genes, age, sex and hormones, liver disease, smoking, diet and some medications all change it [4]. So the result is an estimate. Move the half-life slider to see your best and worst case.

The cutoffs

Each drink is marked OK or Too late using a 2023 meta-analysis of 24 studies. To avoid losing sleep, a 107 mg coffee needed at least 8.8 hours before bed, and a 217.5 mg pre-workout at least 13.2 hours [2]. Drinks over 110 mg get the stricter 13.2-hour cutoff.

There’s no agreed “safe” amount left at bedtime. Lower is better.

The drink amounts

Preset amounts come from the meta-analysis (coffee 107 mg, pre-workout 217.5 mg) [2] and from the FDA’s ranges per 12 fl oz (355 mL) [3]. Where the FDA gives a range, the preset is the middle of it. The actual caffeine in your drink can be much higher or lower, so use the label if there is one.

The FDA says up to 400 mg a day isn’t generally linked to harmful effects in healthy adults [3]. That’s a safety limit, not a sleep target.

More on why this matters: Caffeine cutoff.