Caffeine Calculator

A typical 350 ml mug of filter coffee contains 140 mg of caffeine, while a 190 ml cup of tea has about 50 mg. This means a single mug of filter coffee delivers nearly three times the caffeine of a cup of tea. Instant coffee falls between them at 100 mg per mug. The difference reflects brewing method and leaf or bean type—black teas contain more caffeine than herbal or green varieties, and espresso is concentrated: a 30 ml shot delivers around 75 mg caffeine despite its small volume.

Yes, 400 mg daily is the established safe limit for most healthy adults according to major health organisations. This equates to roughly three large mugs of filter coffee, ten cans of cola, or eight cups of tea spread throughout the day. However, individual tolerance varies—some people experience jitteriness, anxiety, or sleep disruption at lower intakes, while others tolerate higher amounts. Those with hypertension, heart rhythm problems, anxiety disorders, or pregnancy should consult their doctor for personalised advice, as 400 mg may exceed their safe threshold.

Teenagers aged 13–17 should cap intake at 100 mg daily maximum, about one-quarter of the adult limit. Their developing brains are more sensitive to caffeine's effects on sleep and anxiety. High intake during adolescence can disrupt sleep architecture, worsen academic focus, and increase restlessness and stress. For children under 12, avoiding caffeine entirely is recommended. Energy drinks pose particular risk for teens because their high sugar and caffeine combination can mask dangerous consumption levels. Parents should check labels on sports drinks, chocolate-based beverages, and soft drinks.

Caffeine has a half-life of 5–6 hours, meaning half the dose remains active in your bloodstream 5–6 hours after consumption. A 3 p.m. coffee still affects your system at 9 p.m., potentially disrupting sleep onset or quality. Even if your total daily intake is within safe limits, afternoon or evening consumption can trigger insomnia without exceeding your overall dose threshold. For optimal sleep, most sleep specialists recommend avoiding caffeine after 2 p.m., giving your body time to clear it before bedtime. Morning consumption carries minimal sleep risk.

Beyond obvious sources like coffee and tea, caffeine lurks in chocolate, dark chocolate especially at 12 mg per ounce, many soft drinks labelled as cola or cola-flavoured (40 mg per 330 ml can), some sports and energy beverages, instant hot chocolate mixes, and certain medications including some headache remedies, weight-loss pills, and cold medicines. Coffee-flavoured desserts, ice cream, and yoghurt can also contain traces. Always check nutrition labels if you're tracking intake closely. Some prescription and over-the-counter drugs list caffeine as an ingredient to boost efficacy, which can push your daily total higher than expected from beverages alone.

Exceeding 400 mg once or twice poses no serious health risk for most adults. You might experience temporary jitteriness, rapid heartbeat, nausea, or difficulty concentrating, but these effects pass as caffeine is metabolised. The real concern is chronic daily overconsumption: sustained high intake increases anxiety, disrupts sleep quality, elevates resting heart rate, and can worsen digestive issues. Reaching true toxicity (10 grams or about 70 mugs of coffee) is virtually impossible through normal beverages. If you notice persistent anxiety, insomnia, or headaches linked to caffeine intake, reduce your daily amount gradually over a week or two to avoid withdrawal headaches.