How much caffeine do you need?

Dark chocolate 40g 26mg caffeine
Dark chocolate contains caffeine, but only in small amounts – about 26mg for 40g of chocolate, though this varies depending on the percentage of cocoa used in the chocolate. However, if you’re someone who typically can’t resist eating the whole block, you may be getting more caffeine than you realise. The same quantity of milk chocolate contains less caffeine – about 8mg – but it also contains a lot more sugar and fat.
Cup of medium-strength tea 200ml 30mg caffeine
Black and green tea can have anything from 20mg to 45mg of caffeine depending on how long it is brewed for, but even strong tea has less caffeine than an average cup of coffee. A cup that is medium strength (brewed for about five minutes) has on average 30mg of caffeine. Iced tea also contains caffeine – about 28mg per 500ml. Herbal teas such as peppermint and chamomile are caffeine free. Green tea is not.

Diet Coke 375ml 48mg caffeine
Diet Coke may be free from the stimulating effects of sugar but it’s not free from the stimulating effects of caffeine – it contains more than half the caffeine of a Red Bull energy drink. Surprisingly, a can of regular Coke contains about 36mg of caffeine – less than a can of Diet Coke.
Flat white coffee using arabica beans 180ml 60mg caffeine
A regular flat white made with arabica beans (the bean most commonly used in cafes and restaurants) contains 50mg to 90mg of caffeine, the same amount as a latte or cappuccino made with arabica beans.  A cup of instant coffee made with one teaspoon of coffee contains about 70mg of caffeine.
Red Bull 250ml 80mg caffeine
Energy drinks contain large amounts of caffeine as well as sugar or sweeteners and lack any real nutrition. Be aware that some are available in extra-large sizes, so if you are sensitive to caffeine they may leave you open to side effects such as diarrhoea, insomnia and increased heart rate. It’s no surprise these drinks are not sold in school canteens.
Percolated coffee 180ml 105mg caffeine
Nothing beats the aroma of freshly percolated coffee, but it contains an average of 105mg of caffeine per cup, and anywhere up to 150mg per cup. This is because percolated coffee uses the longest brewing method, delicately drawing out the caffeine. The caffeine content could possibly be even higher than this as people making percolated coffee often have a bigger serving – such as a mug  as opposed to an espresso cup.
Fast fact: According to the Mayo Clinic, for most healthy adults, a moderate dose of caffeine – 200mg to 300mg a day – is not harmful. Here, one bean is equal to 15mg of caffeine.