Coffee Caffeine Timing Calculator

About the Coffee Caffeine Timing Calculator

Models how the caffeine from your coffee decays over time, using a typical 5-hour half-life, so you can plan a cut-off before bed.

How to use

Enter the caffeine dose and hours elapsed, then click Calculate.

Worked example

95 mg after 5 hours → about 48 mg remaining.

How to use this calculator

1. Enter the amount of caffeine you consumed.
2. Enter how many hours have passed since you drank it.
3. Choose or enter a half-life value for caffeine.
4. Calculate the remaining caffeine using the decay formula.

The formula explained

• \(\text{Remaining caffeine}\) = the estimated amount of caffeine still in your body
• \(\text{initial caffeine}\) = the caffeine dose you started with
• \(t\) = the time since you drank the coffee, in hours
• \(h\) = the caffeine half-life, in hours

Step by step method

1. Start with the caffeine dose in milligrams. This is the amount right after drinking the coffee.
2. Find the time elapsed since you finished the drink, measured in hours.
3. Use a half-life value to estimate how quickly your body clears caffeine.
4. Plug the values into the formula and compute the remaining amount.

Worked example

Suppose you had a 200 milligram coffee and want to estimate how much is still in your body 6 hours later, using a 5 hour half-life.

1. Set \(\text{initial caffeine} = 200\), \(t = 6\), and \(h = 5\).
2. Compute the exponent: \(\frac{t}{h} = \frac{6}{5} = 1.2\).
3. Calculate \(200 \times \left(\frac{1}{2}\right)^{1.2} \approx 200 \times 0.4353 = 87.1\).

Tips and common mistakes

• Use the caffeine amount from the drink, not the total amount you consumed all day unless that is what you want to estimate.
• Make sure time is entered in hours, not minutes.
• Half-life varies from person to person, so the result is an estimate, not a medical measurement.
• If you are comparing multiple drinks, calculate each one separately and add the remaining amounts.

Frequently asked questions