Is 400 milligrams a bedtime limit?

No. The FDA cites 400 milligrams a day for most adults as an amount not generally associated with negative effects. That is a statement about daily intake, not the last hour before sleep.

Can I be under my daily target and still have a high bedtime estimate?

Yes. A late serving can leave more at bedtime than a larger serving earlier in the day.

Does an app target establish a safe amount?

No. A target organizes the diary. It does not establish a safe intake for your circumstances or replace advice from a health professional.

Does changing half-life change the daily total?

No. The consumed amount stays the same. The estimate of what remains at a later time changes.

Comparison

Daily Caffeine Limit vs Caffeine Left at Bedtime

A 400 milligram daily figure and the caffeine still present at bedtime answer different questions. You can stay under the daily total and still drink late.

Updated October 16, 2026 2 min read

Caffeine Tracker is free to download.

Short answer

A daily limit adds up what you consume. Caffeine left at bedtime is an estimate of what may remain when you usually go to sleep. You can stay under 400 milligrams and still drink late enough that a meaningful share is left at bedtime.

Two days can contain the same caffeine total and still have different estimated amounts left at bedtime. A daily log counts what you had. A bedtime calculation also uses when you had it and the half-life you selected.

We make Caffeine Tracker, which displays both figures. The distinction matters whenever you compare the amount consumed with an estimate for a later hour.

Two numbers for two questions

Figure	Question it answers	Inputs
Daily intake	How much did you log?	Amounts consumed
Bedtime estimate	How much may remain later?	Amounts, times, bedtime, half-life

For example, a single 100 mg serving at 1 pm and the same serving at 6 pm have identical daily totals. They lead to different estimates at an 11 pm bedtime. Keep the amount fixed when you compare timing so you can see what changed.

What a daily limit is for

A daily total adds the caffeine you logged. The FDA cites 400 mg a day for most adults as an amount not generally associated with negative effects. It also says individual circumstances matter. This is a population reference, rather than a personal target.

A catalog entry also estimates the serving. Check the product and amount you actually consumed, and correct a mismatched size before relying on either the daily total or the bedtime figure.

What a bedtime figure is for

A bedtime figure asks how much of today’s caffeine the model still has left at the time you usually sleep. An early 300 milligram total can look modest by bedtime. A smaller drink two hours before bed can look minor on the daily total and large on the bedtime estimate.

The estimate depends on the doses, the times, and the half-life you selected. Change the half-life and the bedtime number moves, even when the drinks stay the same.

How to use the two numbers together

Check the daily total when you want to know whether the day is still inside the limit you chose. Check the bedtime estimate when you are deciding on another serving. A drink can pass one test and fail the other.

If you lower a target later, keep the old entries. The history is what makes the new target meaningful. Deleting the week to tidy the chart removes the comparison you wanted.

Watch both targets on the home screen

Caffeine Tracker compares caffeine consumed with your daily target and estimated caffeine remaining at bedtime with your bedtime target. During setup it can suggest a daily amount from sensitivity, age, and, where it applies, pregnancy or breastfeeding. You can keep that number or replace it.