Caffeine Content Estimator
Estimate total caffeine intake from coffee, tea, espresso, and energy drinks. See how your intake compares to the FDA daily maximum and how long it takes to metabolize.
About this calculator
Caffeine content per ounce varies a lot by beverage -- espresso is brewed under pressure through a small, densely packed puck of grounds, so it comes out far more concentrated per ounce than drip coffee or tea, even though a single shot is a much smaller serving. This calculator multiplies your Number of Servings by Serving Size and by the typical mg-per-ounce figure for your chosen Caffeine Source to estimate Total Caffeine, then compares that to the FDA's commonly cited 400 mg/day guideline for healthy adults.
Hours to Fall Below 10 mg estimates how long your total intake takes to decay past a 10 mg residual -- roughly the caffeine in a few sips of coffee -- using caffeine's average biological half-life of about 5 hours -- the time for roughly half of it to clear your system -- though individual metabolism varies with genetics, pregnancy, liver function, and other medications, so treat this as a rough estimate rather than a personalized clearance time. Raising either Number of Servings or Serving Size always raises Total Caffeine and, with it, the percentage of the daily maximum.
Inputs
Results
Total Caffeine
192 mg
Figures current as of 2026. Source: U.S. Food and Drug Administration consumer guidance, "Spilling the Beans: How Much Caffeine is Too Much?"
How to Use This Calculator
- Select the caffeine source (drip coffee, espresso, black tea, green tea, or energy drink).
- Enter the number of servings and serving size in ounces.
- The calculator shows total caffeine in mg, per-serving amount, percentage of the 400 mg FDA daily maximum, and hours to fall below 10 mg.
- Compare your total against the FDA's 400 mg/day reference point for healthy adults -- it is a population guideline, not a personal safe limit, and pregnant people and those on certain medications are usually advised to stay well below it.
- Check Hours to Fall Below 10 mg against your bedtime; caffeine taken 6 hours before bed has been shown to measurably disrupt sleep.
How the result changes with Number of Servings
| Number of Servings | Total Caffeine |
|---|---|
| 1 | 96 mg |
| 1.5 | 144 mg |
| 3 | 288 mg |
| 5 | 480 mg |
What each input means
- Caffeine Source
- The type of caffeinated beverage.
- Number of Servings
- How many servings you consume.
- Serving Size (oz)
- Volume of one serving in ounces. A standard cup is 8 oz, espresso shot is ~1 oz.
How this is calculated
Worked example, using the default values
- Identify Input ParametersCaffeine Source = 1, Number of Servings = 2, Serving Size (oz) = 8 = 3 input(s) provided
- Calculate Total Caffeine192 = 192
- Calculate Per Serving96 = 96
- Calculate % of FDA Daily Max% of FDA Daily Max48 = 48
Figures and sources
- FDA 400 mg/day caffeine guideline for healthy adults (2026) — U.S. Food and Drug Administration consumer guidance, "Spilling the Beans: How Much Caffeine is Too Much?"
Engine last updated . Checked against 5 independently-derived tests — how we verify calculators. Built by Paul Gunder, a software engineer, not a licensed financial, medical, or legal professional.
Frequently Asked Questions
Why does espresso have so much more caffeine per ounce than drip coffee?
Espresso is forced through a small amount of finely ground, tightly packed coffee under pressure, extracting far more caffeine per ounce of liquid than drip brewing does. A single espresso shot is a much smaller serving, though, so a full cup of drip coffee can still contain more total caffeine than one shot.
Is the 400 mg FDA daily maximum a hard limit?
It's the amount the FDA has said is not generally associated with dangerous or negative effects for most healthy adults -- not a universal safe limit. Pregnant people, those sensitive to caffeine, and people on certain medications are often advised to stay well below it; check with a healthcare provider for personal guidance.
How accurate is the Hours to Fall Below 10 mg estimate?
It uses caffeine's commonly cited average half-life of about 5 hours to estimate when your intake decays below a 10 mg residual (it reads 0 when you started below that). Real half-life varies widely by person -- roughly 1.5 to 9.5 hours depending on genetics, liver function, pregnancy, and other factors -- so this is a general estimate, not a personalized clearance time.
Does the calculator account for how strong I brew my coffee?
No -- it uses a typical mg-per-ounce figure for each source, which represents an average strength. A stronger or weaker brew than typical for that method will contain more or less caffeine than the estimate, so treat the result as a reasonable ballpark rather than an exact measurement of your specific cup.
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