Timing matters, and people differ

Caffeine Cutoff Calculator

How much of that afternoon caffeine might still be around at bedtime? Enter up to three servings, compare different metabolism assumptions, and explore a cutoff for a separate single-drink example.

An estimate, not a sleep guarantee. This adult educational tool uses a simplified half-life model. It cannot measure your metabolism, predict your sleep, or identify a caffeine amount that is safe for you. Pregnancy, medications, health conditions, smoking changes, and other factors can alter caffeine clearance. Follow individual medical advice.

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1. Set bedtime and a model assumption

Planned bedtime (required)

Half-life for the main estimate

Half-life is the time it takes for the modeled caffeine amount to fall by half. Five hours is a starting assumption, not a personal measurement. The comparison below uses 3, 5, 7, and 9 hours as examples; your actual half-life may fall outside them. These are not confidence intervals.

2. Enter your caffeine servings

Use milligrams from the product label or retailer when available. Coffee and tea vary widely with size and preparation. Include relevant energy drinks, pre-workout products, and other sources; do not change medicines based on this tool.

Choose the calendar day explicitly. “Bedtime day” means the date on which the planned bedtime occurs. For a bedtime after midnight, an afternoon drink may belong to the previous day. Blank optional amounts are ignored.

Serving 1 (required)

Caffeine (mg)

Time consumed

Day consumed

Description (optional)

Serving 2 (optional)

Caffeine (mg)

Time consumed

Day consumed

Description (optional)

Serving 3 (optional)

Caffeine (mg)

Time consumed

Day consumed

Description (optional)

Amounts are entries for calculation, not recommended doses. The tool includes only the listed servings; caffeine from earlier days or unlisted sources may add to the actual amount.

3. Explore a single-drink cutoff

This separate what-if works backward from a drink’s dose and a chosen mathematical target. It does not include the servings above or identify a level that won’t affect sleep.

Example drink dose (mg)

Illustrative remaining amount at bedtime (mg)

The 25 mg default is an arbitrary example, not a medically established sleep-safe threshold. Lower numbers require more time in the model; they do not guarantee better sleep.

Your modeled bedtime estimate

Each row is a different assumption applied to all entered servings.
Assumed half-life	Caffeine remaining at bedtime

Separate single-drink cutoff

This is not a recommended last-drink time. Other servings can push the total higher. Caffeine effects and the amount remaining are not interchangeable.

Your editable summary

Review and edit before printing or downloading. Changing the form requires recalculation; direct summary edits are replaced only after confirmation.

Caffeine timing summary

How to use the estimate

A half-life is not a disappearance time. In a 5-hour model, 100 mg becomes 50 mg after 5 hours and 25 mg after 10 hours.
No universal cutoff guarantees sleep. Dose, timing, individual response, and other factors matter. A small modeled remainder is not proof that caffeine is having no effect.
Daily intake and sleep effects are different questions. FDA cites 400 mg per day as an amount not generally associated with negative effects for most adults. It is not a sleep-friendly target or an individual safety limit.
Try a gentle change. If appropriate, test an earlier last serving and track how you feel. Regular users may experience withdrawal if intake drops abruptly; ask a clinician or pharmacist about a gradual approach when needed.

Model: remaining mg = dose × 0.5^(hours elapsed ÷ half-life). The model assumes immediate absorption and simple exponential elimination. It ignores absorption delays, active metabolites, and individual variation; it does not estimate blood concentration or clinical risk.

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Sources: CDC/NIOSH: Caffeine and sleep ; National Academies: Pharmacology of caffeine ; FDA: How much caffeine is too much? . Scenario values and illustrative targets are planning choices.