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Caffeine Half-Life Calculator

Calculate how long caffeine stays in your system. Free caffeine half-life calculator with metabolism visualization and sleep impact analysis.

Calculators
Instant results
mg
at:
Average: 5 hours (3-7 range)
2h (fast metabolizer)10h (slow metabolizer)
Total Intake
95 mg
Peak Level
95 mg
at 8:00 AM
At Bedtime (10 PM)
14 mg
Sleep-Safe Time
1:00 PM
below 50 mg

Caffeine Level Throughout the Day

50mg sleep threshold
12:00 AM
0 mg
0
1:00 AM
0 mg
2:00 AM
0 mg
3:00 AM
0 mg
3
4:00 AM
0 mg
5:00 AM
0 mg
6:00 AM
0 mg
6
7:00 AM
0 mg
8:00 AM
95 mg
9:00 AM
83 mg
9
10:00 AM
72 mg
11:00 AM
63 mg
12:00 PM
55 mg
12
1:00 PM
48 mg
2:00 PM
41 mg
3:00 PM
36 mg
15
4:00 PM
31 mg
5:00 PM
27 mg
6:00 PM
24 mg
18
7:00 PM
21 mg
8:00 PM
18 mg
9:00 PM
16 mg
21
10:00 PM
14 mg
11:00 PM
12 mg
Above 50mg (daytime) Above 50mg (nighttime) Below 50mg

Caffeine Guidelines

  • FDA recommends a maximum of 400mg per day for healthy adults
  • Caffeine half-life averages 5 hours but varies from 3-7 hours based on genetics, age, and medications
  • Sleep experts suggest keeping caffeine below 50mg at bedtime
  • Pregnant women should limit intake to 200mg per day
  • Caffeine takes 30-60 minutes to reach peak blood levels after consumption
  • Smoking can halve caffeine half-life; oral contraceptives can double it

About Caffeine Half-Life Calculator

This tool calculates how caffeine levels decrease in your body over a 24-hour period using exponential decay based on the half-life of caffeine. The default half-life is 5 hours, meaning after 5 hours, half the caffeine is still in your system. Adjust the half-life slider to match your metabolism. All calculations happen in your browser.

How to Use Caffeine Half-Life Calculator

1

Enter your values

Open Caffeine Half-Life Calculator and enter the values you want to calculate or convert.

2

Select units or options

Choose the input and output units, formats, or calculation parameters.

3

View results instantly

Results are calculated in real-time as you type — no submit button needed.

4

Copy or use the result

Copy the calculated result or use it directly in your work.

Frequently Asked Questions

Caffeine half-life is the time it takes for your body to eliminate half the caffeine in your system. For most adults, caffeine's half-life is about 5-6 hours, meaning if you consume 200mg of caffeine, you'll still have about 100mg in your system 5-6 hours later.