A starting caffeine dose for your weight, in cups of coffee, espresso or tea, and when to take it. Runs in your browser; nothing is saved or sent.
What this does: gives you a starting caffeine dose for a long run or race, based on your body weight, and shows what that is in cups of coffee, espresso shots or tea, when to take it, and the most to have in a day. It’s for healthy adult runners and endurance athletes who already drink coffee or tea, or want to try caffeine before a run. Enter your weight, and your start time if you want a clock time to aim for. Caffeine is a stimulant found naturally in coffee, tea and cocoa. Doses are worked out in mg/kg: milligrams of caffeine per kilogram of body weight.
How it works
The International Society of Sports Nutrition’s position stand (its expert summary of the research) on caffeine (Guest et al., 2021) reports that caffeine has consistently improved exercise performance at 3–6 mg per kg of body weight, that the smallest helpful dose may be as low as 2 mg/kg, and that very high doses (about 9 mg/kg) bring a high rate of side effects without extra benefit. The most common timing in studies is about 60 minutes before exercise, and aerobic endurance shows the most consistent benefit. Across 46 studies, moderate doses (3–6 mg/kg) improved the time to finish a set distance as fast as possible (a time trial) by about 2%, and average power output by about 3% (Southward et al., 2018). Coffee works as a source too: 5 of 9 studies of caffeinated coffee found better endurance performance (Higgins et al., 2016).
We start you at 2–3 mg/kg, capped at 200 mg. The European Food Safety Authority found single doses up to 200 mg (about 3 mg/kg) raise no safety concerns for healthy adults, including within two hours before intense exercise, and up to 400 mg a day, spread through the day, raises none for healthy adults other than during pregnancy (EFSA, 2015). The U.S. Food and Drug Administration cites 400 mg a day as an amount not generally linked to negative effects for most healthy adults (FDA, 2024), so the studied range here stops at 400 mg. Response varies from person to person; if you drink coffee daily you already know how you respond, and starting at the low end still makes sense. Doses of 1–3 mg/kg also appear to help (Guest et al., 2021), so the starting dose may be all you need.
Caffeine in everyday drinks
Drink
Serving
Caffeine
Brewed coffee
8 fl oz cup
about 95 mg
Espresso
1 fl oz single shot
about 63 mg
Black tea, brewed
8 fl oz cup
about 47 mg
Green tea, brewed
8 fl oz cup
about 29 mg
Decaf coffee
8 fl oz cup
about 2 mg
Values from USDA FoodData Central. Coffee varies a lot by bean, brew and size: café and large-size coffees can contain two to three times as much, so use your usual drink and treat the servings as an estimate.
Using it well
Try it in training first, at the same time and with the same drink you’ll use on race morning.
Count every source across the day, including tea and any other caffeinated drinks.
Mind your sleep. Your body takes several hours to clear half of a dose, so an afternoon or evening run’s caffeine can still be around at bedtime; EFSA notes that 100 mg close to bedtime may affect sleep in some adults.
Back off if it doesn’t sit well. If you feel jittery, queasy or your heart races, have no more caffeine that day and drink some water. Too much caffeine can cause a fast heartbeat, anxiety, an upset stomach and headaches (FDA).
Guest NS, et al. International Society of Sports Nutrition position stand: caffeine and exercise performance. J Int Soc Sports Nutr. 2021;18:1. Source
Southward K, Rutherfurd-Markwick KJ, Ali A. The effect of acute caffeine ingestion on endurance performance: a systematic review and meta-analysis. Sports Med. 2018;48(8):1913–1928. Source
Higgins S, Straight CR, Lewis RD. The effects of preexercise caffeinated coffee ingestion on endurance performance: an evidence-based review. Int J Sport Nutr Exerc Metab. 2016;26(3):221–239. Source
European Food Safety Authority. Caffeine: EFSA explains risk assessment (2015), summarizing the EFSA NDA Panel’s Scientific Opinion on the safety of caffeine, EFSA Journal 2015;13(5):4102. Source
U.S. Food and Drug Administration. Spilling the beans: how much caffeine is too much? (2024). Source
U.S. Department of Agriculture, Agricultural Research Service. FoodData Central (food composition database). Source
General information for healthy adult runners, not medical advice. If you have a medical condition, take regular medicine, or are pregnant or breastfeeding, talk to your doctor before using caffeine for training.