Caffeine calculator for athletes

How the caffeine calculator works

Caffeine is one of the few supplements with strong evidence for endurance performance. It makes hard efforts feel easier and helps you hold power for longer. The International Society of Sports Nutrition (ISSN) recommends 3 to 6 mg per kg of body weight, most commonly taken about 60 minutes before exercise. This tool is one of the free LeCoach cycling calculators.

The calculator sets your dose from your weight and how strongly caffeine affects you: 2 mg/kg if it affects you strongly, 3 mg/kg if normally and 4 mg/kg if it affects you little. It rounds to 10 mg and never goes above 400 mg. It then works out when to take it and how much is still in your body at bedtime, using an average half-life of 5 hours.

Caffeine dose by body weight

The upper end is capped at 400 mg, the daily limit for healthy adults. The ISSN notes that doses as low as 2 mg/kg may also work, and that very high doses, around 9 mg/kg, cause side effects in many people. More is not better.

Coffee varies a lot from cup to cup. Gels and tablets list their dose on the pack, which makes them easier to measure.

Safety first

• Stay under 400 mg a day from all sources. The European Food Safety Authority (EFSA) considers up to 400 mg a day, and single doses up to 200 mg (about 3 mg/kg), no safety concern for healthy adults. If you are new to caffeine, start below 200 mg.
• Not for everyone. Do not use caffeine to boost performance if you are under 18, pregnant (EFSA advises no more than 200 mg a day in pregnancy) or have a heart condition. If you take regular medication or are unsure, ask your doctor first.
• Know the side effects. Jitters, a racing heart, an upset stomach, anxiety and poor sleep are all signs you took too much. Stop and take less next time.
• Test it in training first. Never try a new dose, product or timing on race day.

Timing for long events

Caffeine has a half-life of about 4 to 6 hours, though it ranges from 1.5 to 10 hours between people. A dose taken an hour before the start is still working for much of a morning race: with a 5-hour half-life, about 115 mg of a 230 mg dose remains 5 hours later.

For events that last many hours, some athletes keep part of their dose for later, for example a caffeinated gel in the final hours when fatigue builds. If you do this, count every gel, drink and coffee towards your daily total, and use amounts you have tested in training. The race nutrition calculator helps you plan the carbs and fluid that go with it, and our guide to race fueling for cyclists covers the whole race-day plan.

Sleep is the usual trade-off. With a 5-hour half-life, 230 mg takes about 11 hours to drop below 50 mg. For afternoon and evening races, a smaller dose or an earlier one protects your night. Read more in sleep and recovery for cyclists.

If you drink coffee every day

Many athletes wonder whether they should stop coffee before a race to get a bigger effect. The evidence on whether daily users get a smaller boost is not settled, and stopping suddenly can cause headaches and tiredness for a few days. A simple approach: keep your normal routine, count your usual coffee in your daily total, and test your race dose in training.

Common mistakes

• Trying caffeine for the first time on race day. Your stomach and heart rate may react in ways you did not expect.
• Forgetting the breakfast coffee. It counts towards the 400 mg.
• Stacking gels without counting. Several caffeinated gels plus a pre-race dose can add up fast.
• Taking it too late. A late-afternoon dose can cost you sleep, which costs you recovery.
• Chasing a bigger dose. Above your tested amount, side effects rise faster than benefits.

Add your caffeine plan to the race day checklist. You can ask LeCoach how to plan race-day fuel, caffeine included, and it answers from your race distance and your own rides.