Transparent caffeine math

Caffeine Half-Life Worksheet

Enter a caffeine amount, elapsed time, and half-life assumption to see the model's estimate.

Your inputs

Use the amount on a product label or another source you trust. Phase & Leaf products are not assigned measured amounts here.

Choose a value from 0 to 24 hours.

Half-life assumption

The 4 to 6 hour range is a general adult benchmark, not a personal measurement.

Model estimate

Caffeine remaining

50 mg

Estimated caffeine remaining: 50 mg after 5 hours, using a 5-hour half-life assumption.

Estimated caffeine remaining over 24 hours A declining curve from 100 mg at hour zero to 3.6 mg at hour 24. 0 12 24 h 100% 50% 0%
HourEstimated amount
0100 mg
457.4 mg
833 mg
1218.9 mg
1610.9 mg
206.3 mg
243.6 mg

Show the work

Method and limitations

Formula and inputs

Formula: remaining amount = starting amount × 0.5(elapsed hours ÷ half-life hours).

The starting amount comes only from your input. The selected 4, 5, or 6 hour half-life is an assumption. The chart applies the same formula from hour 0 through hour 24.

Sources and boundaries

The U.S. Food and Drug Administration notes that caffeine response and sensitivity vary. The National Library of Medicine's 2023 StatPearls review describes an average adult half-life near five hours, while a separate StatPearls review gives a typical adult range of four to six hours.

This is arithmetic, not testing. It does not account for individual metabolism, medicines, pregnancy, health conditions, serving variability, or multiple caffeine servings. It does not provide medical advice.

Shop by phase

Choose the drink. Enter the amount yourself.

Morning Push Coffee 12 oz exact-label package mock-up

Morning Push Coffee

Ground coffee for the first cup of the day.

$29.99 · Available

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Midday Matcha green tea powder in a 1 oz pouch

Midday Matcha

Matcha green tea powder for a whisked cup or latte.

$27.99 · Available

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Later Hojicha 3 oz pouch beside a prepared amber cup, roasted green tea powder, and a whisk

Later Hojicha

Stone-milled roasted green tea powder for a warm or iced cup.

$27.99 · Available

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Product caffeine amounts are not listed because Phase & Leaf does not have matching finished-product assay data for these preparations.

Worksheet FAQ

Before you use the estimate

Does this tell me when to stop drinking caffeine?

No. It shows arithmetic under the inputs you choose. It does not set a personal cutoff.

Does Phase & Leaf measure the caffeine in each product?

No matching finished-product assay is used here. Enter an amount from a label or another source you trust.

Why can I choose 4, 5, or 6 hours?

Published clinical references describe adult caffeine half-life around this general range. Individual response can differ.