Caffeine Intake Calculator

What this calculator does

Find out how much caffeine your drinks add up to in a day. It adds up quietly. A large coffee in the morning, a tea after lunch and a soft drink later can total more than you'd expect. The calculator adds up the caffeine from the drinks you list. Then it compares the total with a daily limit you choose. The limit starts at 400 mg a day, the figure the US Food and Drug Administration (FDA) gives for healthy adults.

You can change every amount per serving. The starting values are the middle of the ranges the FDA gives for a 12-ounce serving. But real drinks vary a lot by brand, brewing method and cup size. So the label, or the café's posted figure, is always the better number to use.

Where it's used

Why this math matters outside the classroom:

• Daily tally. Someone who drinks two 12-ounce coffees at 180 mg each and one 53 mg soft drink adds 360 + 53 to get 413 mg.
• Swapping drinks. A student trading an afternoon energy drink (144 mg) for green tea (37 mg) cuts 107 mg from the day's total.
• Reading labels. Shoppers compare the caffeine printed on two cans to see which brand has less per serving.
• Office coffee orders. A team member counts how many cups a pot serves and how much caffeine each cup holds.
• Health class. Students list a day's drinks and total their caffeine to practise multiplying and adding with real labels.

Grade level and standards: Grade 4; Common Core State Standards for Mathematics 4.OA.A.3. © Copyright 2010. National Governors Association Center for Best Practices and Council of Chief State School Officers. All rights reserved.

How to use it

1. Enter how many servings of each drink you had. Half servings are fine.
2. When you know it, replace the caffeine per serving with the figure from the label or menu. Use Other source for espresso shots, chocolate or anything else.
3. Set the daily limit you want to compare with. It starts at 400 mg. Change it if your doctor has suggested a different amount.
4. Read the total, how much is left (or how far over you are) and the share of your limit used.

What the inputs mean

Brewed coffee (12 fl oz): servings

One serving here is 12 fluid ounces, a typical mug. A large café cup is often 16 to 20 ounces, which is 1⅓ to 1⅔ servings.

Brewed coffee (12 fl oz): caffeine per serving

The FDA gives a range of 113 to 247 mg for 12 ounces of brewed coffee. 180 mg is the middle of that range.

Caffeinated soft drink (12 fl oz): caffeine per serving

The FDA gives 23 to 83 mg for a 12-ounce soft drink with caffeine. 53 mg is the middle of that range. Many soft drinks have no caffeine at all.

Energy drink (12 fl oz): caffeine per serving

The FDA gives 41 to 246 mg for 12 ounces of energy drink. 144 mg is roughly the middle. The can's label is the best source.

Other source: caffeine per serving

Use this for anything not listed, such as a shot of espresso, chocolate or a caffeine tablet. Enter the amount from its label.

Daily limit to compare with

The FDA says 400 mg a day is an amount not generally linked to negative effects in healthy adults. People react to caffeine differently. If you're pregnant, nursing, taking medication or have a health condition, ask your doctor what limit is right for you.

Formula and method

caffeine from a drink = servings × caffeine per serving
total = sum of the caffeine from every drink
left before limit = limit − total
share of limit = total ÷ limit × 100

Each drink's caffeine is the number of servings times the milligrams (mg) in one serving. The calculator adds those amounts and takes the total away from your limit. If the result is below zero, it's shown as the amount you're over the limit.

The total is shown to the nearest milligram. The amount per serving can differ by two times or more between products. So treat the result as an estimate unless you use label values.

Worked example

Someone has one 12-ounce mug of brewed coffee, one 12-ounce green tea and one 12-ounce caffeinated soft drink, using the default amounts and a 400 mg limit.

1. Coffee: 1 × 180 mg = 180 mg.
2. Green tea: 1 × 37 mg = 37 mg.
3. Soft drink: 1 × 53 mg = 53 mg.
4. Total: 180 + 37 + 53 = 270 mg. Left before the limit: 400 − 270 = 130 mg, so 67.5% of the limit is used.

Result: The day's drinks contain about 270 mg of caffeine, 130 mg under the 400 mg limit.

Understanding the result

The result is a tally, not a health check. Staying under the number you set doesn't mean every amount is right for everyone. Going over it is a nudge to check your own sources, not a diagnosis.

Caffeine from late-day drinks stays in your body for hours. So for sleep, when you have your drinks can matter as much as the total.

Assumptions and limitations

• One serving is 12 fluid ounces for the listed drinks, matching the FDA's figures.
• Default amounts are the middle of the FDA's ranges. Real products may be higher or lower.
• All drinks are had on the same day.
• The calculator doesn't know specific brands or café sizes. Enter label values for accuracy.
• It gives no medical advice or personal limit. Questions about caffeine and pregnancy, medication or health conditions belong with a doctor.
• Caffeine in foods and medicines counts only if you enter it under Other source.

Frequently asked questions

Sources

• US FDA: Spilling the Beans: How Much Caffeine Is Too Much? (checked 2026-10-19)

How this calculator is checked

Method: Sum of servings × caffeine per serving; default amounts and the 400 mg reference from the US FDA consumer update 'Spilling the Beans' (updated 2024-08-28). The calculation is covered by automated tests with known reference values and edge cases. Last updated 2026-10-18. Found a problem? Tell us.

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