To calculate caffeine half life enter initial caffeine amount in milligrams (mg) consumed and hours elapsed since consumption in calculator, Typical values range from 3 to 6 hours.

You will see remaining caffeine amount in milligrams along-with starting dose, time passed, caffeine remaining, and the formula used. (Remaining Caffeine = Initial Dose × (1/2)^(Elapsed Time / Half-Life)

The initial dose is 150 mg, and half-life is 5 hours. After 1 half-life (5 hours), remaining amount is calculated as 150 × (1/2) = 75 mg. After 2 half-lives (10 hours), amount decreases further to 75 × (1/2) = 37.5 mg. Finally, after 3 half-lives (15 hours), remaining quantity is 37.5 × (1/2) = 18.75 mg.

Time Passed (Hours)	Caffeine Remaining (mg)	Time Passed (Hours)	Caffeine Remaining (mg)
0 (Initial Dose)	100 mg	25	1.56 mg
1	87.87 mg	26	1.37 mg
2	77.19 mg	27	1.19 mg
3	67.87 mg	28	1.03 mg
4	59.92 mg	29	0.89 mg
5	50 mg	30	0.78 mg
6	43.94 mg	31	0.68 mg
7	38.58 mg	32	0.59 mg
8	33.87 mg	33	0.51 mg
9	29.73 mg	34	0.44 mg
10	25 mg	35	0.39 mg
11	21.97 mg	36	0.34 mg
12	19.25 mg	37	0.29 mg
13	16.86 mg	38	0.25 mg
14	14.78 mg	39	0.22 mg
15	12.5 mg	40	0.20 mg
16	10.98 mg	41	0.17 mg

Caffeine Half-Life Formula

Remaining = Initial × (0.5)^(Elapsed / HalfLife)

Where:

• Initial: Starting caffeine dose in mg
• Elapsed: Hours since consumption
• HalfLife: Average caffeine half-life of 5.7 hours
• (0.5): Fraction remaining after each half-life

For 400 mg caffeine, 8 hours elapsed: 400 × (0.5)^(8 / 5.7) ≈ 164.2 mg remaining

How to Calculate How Long Caffeine Lasts?

To estimate how long caffeine lasts, use the starting amount and time since consumption in formula: Remaining = Initial × (0.5)^(Elapsed / 5.7)

A 250 mg caffeine, 6 hours later: 250 × (0.5)^(6 / 5.7) ≈ 124.2 mg left

• 100 mg, after 3 hours: 100 × (0.5)^(3 / 5.7) ≈ 69.2 mg
• 300 mg, after 12 hours: 300 × (0.5)^(12 / 5.7) ≈ 68.9 mg
• 175 mg, after 9 hours: 175 × (0.5)^(9 / 5.7) ≈ 58.9 mg

How long does it take for 200 mg of caffeine to wear off?

For most people, the noticeable effects of 200mg of caffeine will start wearing off after about 6-8 hours. You may still feel mild effects until the caffeine is fully metabolized, which typically takes around 10-12 hours.

For optimal sleep, it’s best to avoid consuming your 200mg caffeine dose within 8-10 hours of bedtime.

What is Caffeine Half-Life?

Caffeine Half-Life is the time required for the amount of caffeine in the body to decrease by 50%. In healthy adults, caffeine’s half-life averages about 5-6 hours.

After one half-life, 50% of the initial dose remains. After two half-lives, 25% is left. This continues until elimination is complete, usually after 4-5 half-lives.