Skip to content
Calculation Machine

Caffeine Limit Calculator

Your safe daily caffeine ceiling and how many coffees or energy drinks that is.

Reviewed by James Whitfield · How we check our maths

Your values

ⓘ Live results

Results
Safe daily limit
400 mg
Consumed so far
285 mg (71% of limit)
Headroom left
115 mg (1.2 more cups)
Performance dose
225 - 450 mg, 45-60 min before
Still active at bedtime
94 mg
Sleep-safe cut-off
12.6 hours before bed

Working

  1. 1limit = min(400, 6 x 75) = 400 mg
  2. 2half-life 5 h: 285 x 0.5^(8/5) = 94 mg left

Quick answer

Healthy adults tolerate about 400 mg of caffeine a day, or roughly 6 mg per kg. Performance dosing is 3 to 6 mg/kg taken 45 to 60 minutes before effort.

The formula

limit mg = min(400, 6 x kg)

Worked example

Worked example

Using the values the calculator loads with.

Inputs

  • Body weight75 kg
  • Coffees today3 cups
  • Caffeine per cup95 mg
  • Hours until bedtime8 hours

Result

  • Safe daily limit400 mg
  • Consumed so far285 mg (71% of limit)
  • Headroom left115 mg (1.2 more cups)
  • Performance dose225 - 450 mg, 45-60 min before
  • Still active at bedtime94 mg
  • Sleep-safe cut-off12.6 hours before bed

How to use the Caffeine Limit Calculator

  1. 1Enter your weight, then how much caffeine you have already had today.
  2. 2Set hours until bedtime to see what will still be circulating when you try to sleep.
  3. 3Keep the pre-bed residue under about 50 mg for undisturbed sleep.

Frequently asked questions

Is 400 mg safe for everyone?

No. Pregnancy guidance is 200 mg, and people with heart conditions, anxiety or on certain medicines should ask a doctor for a lower ceiling.

How long does caffeine stay in your system?

The half-life averages five hours, so a quarter of a 3 pm coffee is still active at 1 am for many people.

About this calculator