# Coffee Calculator – How Much Caffeine Do I Need?

URL: https://speedycalculator.com/calculators/food/coffee/
Last updated: 2026-10-30

> The coffee calculator works out a sensible caffeine dose for your body weight and goal – alertness, strong focus or sports performance – adjusted for how sensitive you are to caffeine, how many servings of your drink that is, and how it compares with the 400 mg daily limit.

## Inputs

- Body weight (kg, lb)
- Goal
- Caffeine sensitivity
- Drink
- Caffeine per serving (custom) (mg)
- Servings already today
- Pregnant or breastfeeding?

## Results

- Caffeine per serving
- Suggested caffeine dose now
- Servings of your drink for that dose
- Caffeine so far today
- Servings left before the daily limit
- Daily limit

## Formula

```
Dose (mg) = body weight (kg) × target (1.5 mg/kg for alertness, 3 mg/kg for strong focus, 4.5 mg/kg for exercise) × sensitivity factor
Single dose kept ≤ 200 mg (EFSA); daily total ≤ 400 mg (FDA, EFSA); 200 mg in pregnancy
Servings = dose ÷ caffeine per serving
```

## Explanation

Caffeine starts working in 15–45 minutes and its effect lasts about 3–5 hours; its half-life is around 5 hours, so an afternoon coffee can still affect your sleep at night. Sensitivity varies a lot from person to person.

### How to use the Coffee Calculator – How Much Caffeine Do I Need?

- **Body weight**
- **Goal**
- **Caffeine sensitivity**
- **Drink**
- **Caffeine per serving (custom)**
- **Servings already today**
- **Pregnant or breastfeeding?**

Results update as you type, and every field accepts the units shown in its menu.

### How it works

Enter your weight, choose your goal, sensitivity and drink, and how many servings you have had today.

### Tips

- Weigh coffee beans rather than using scoops – roast level and grind change how much a scoop holds.
- Grind just before brewing and match the grind size to the method (fine for espresso, coarse for French press and cold brew).
- Use filtered water just off the boil (90–96 °C / 195–205 °F) for hot coffee.
- Adjust the ratio to taste in small steps – one change at a time.

### Common mistakes to avoid

- Using boiling water on green or white tea, which turns it bitter.
- Forgetting that caffeine content varies widely between drinks and brands.
- Comparing ratios written different ways (1:16 coffee:water vs 60 g per litre).

### Inputs explained

FieldWhat to enterBody weightUnits: kg, lbGoalChoose one: Stay alert, Strong focus, Exercise performanceCaffeine sensitivityChoose one: Very tolerant, Tolerant, Average, Sensitive …DrinkChoose one: Brewed (drip) coffee, 8 oz / 237 ml, Espresso, single shot (1 oz), Espresso, double shot, Americano, 12 oz (2 shots) …Caffeine per serving (custom)In mgServings already todayA numberPregnant or breastfeeding?Choose one: No, Yes

### What each result means

- **Servings of your drink for that dose** = [Suggested caffeine dose now]÷[Caffeine per serving]
- **Caffeine so far today** = [Servings already today]×[Caffeine per serving]

### Example values

How the main result changes when **Body weight** changes and everything else stays at the example values above:

Body weight (kg)Suggested caffeine dose now (mg)355352.5797010587.5131105158140200

## Worked example

Inputs — Body weight: 70 kg; Goal: Stay alert; Caffeine sensitivity: Average; Drink: Brewed (drip) coffee, 8 oz / 237 ml; Servings already today: 1; Pregnant or breastfeeding?: No.

Results — Caffeine per serving = 95 mg; **Suggested caffeine dose now = 105 mg**; Servings of your drink for that dose = 1.1; Caffeine so far today = 95 mg; Servings left before the daily limit = 3.2; Daily limit = Within the daily limit.

## FAQ

**How much caffeine is too much?**
The FDA and EFSA say up to 400 mg a day is safe for most healthy adults; 200 mg in pregnancy.

**How much caffeine is in a cup of coffee?**
About 95 mg in 8 oz of brewed coffee, 63 mg in a single espresso.

**How long does caffeine last?**
Its half-life is about 5 hours, so half is still in your body 5 hours later.


## Sources

- [U.S. FDA – Spilling the beans: how much caffeine is too much?](https://www.fda.gov/consumers/consumer-updates/spilling-beans-how-much-caffeine-too-much)
- [EFSA – Scientific opinion on the safety of caffeine](https://www.efsa.europa.eu/en/efsajournal/pub/4102)