Fitness formulas: protein, water, creatine and caffeine

Body-weight-based formulas provide a quick way to estimate sports nutrition needs. They offer simple benchmarks for protein, water, calories and certain supplements. However, a fitness formula is only a starting point: activity level, sweating, diet, sleep and your specific goal will always influence the final result.

Why use weight-based formulas

Two people with very different body weights generally do not have the same needs. Multiplying a reference amount by body weight therefore provides a more individualized estimate than a one-size-fits-all recommendation.

These calculations are especially useful for setting an initial measurable target. You should then monitor recovery, performance, digestion, hunger and weight changes over several weeks so you can gradually adjust the amounts.

• Use your current body weight as the calculation basis.
• Apply the formula that matches your goal.
• Keep the same target for two to three weeks.
• Adjust based on your results and how you feel.

Calculate your protein needs

For someone who trains regularly, a daily intake of 1.4 to 2 g of protein per kilogram of body weight suits most situations. The upper end of the range is particularly relevant for strength training, muscle gain or a calorie-deficit phase.

The protein formula

Body weight in kg × 1.4 to 2 g

For a 70 kg person, this amounts to approximately 98 to 140 g of protein per day. The basic formula uses 2 g per kilogram, or 140 g. This target is a reasonable benchmark for an active person who wants to build or preserve muscle mass.

Distributing protein across three to five intakes generally makes it easier to consume. A portion of 20 to 40 g per meal may be suitable, but total daily intake remains the priority.

Estimate your daily water needs

The formula of 35 mL of water per kilogram of body weight provides a practical baseline. For 70 kg, this equals 2.45 liters per day. This estimate must account for real-world conditions: temperature, workout duration, sweating, altitude and the water content of food.

The hydration formula

Body weight in kg × 35 mL

European reference values for total water intake are approximately 2 liters per day for an adult woman and 2.5 liters for an adult man. These amounts include water from beverages and food. Needs increase during prolonged exercise or in hot weather.

To assess fluid loss during a workout, you can weigh yourself before and after training. A loss of more than approximately 2% of body weight generally indicates that hydration should be improved.

Calculate your calories based on your goal

Calories per kilogram provide a quick estimate of energy needs. They do not replace an individualized calculation that accounts for age, height, sex, body composition, occupation and training volume.

• Maintenance: approximately 30 kcal × body weight.
• Fat loss: approximately 22 to 25 kcal × body weight.
• Muscle gain: approximately 35 to 40 kcal × body weight.

For 70 kg, these shortcuts give approximately 2,100 kcal for maintenance, 1,540 to 1,750 kcal for fat loss and 2,450 to 2,800 kcal for muscle gain. These figures are initial estimates, not universal prescriptions.

Calorie needs change with body weight and activity. A dynamic tool such as the NIDDK Body Weight Planner provides a more personalized projection than simply multiplying by body weight.

Adjust calories based on your results

Weigh yourself under similar conditions several times a week, then track the average. If your weight and measurements remain stable despite a fat-loss or weight-gain goal, adjust your intake in small increments rather than changing your diet abruptly.

Determine your creatine dose

Creatine monohydrate is one of the best-documented ergogenic aids for repeated high-intensity efforts and strength training. A commonly used maintenance formula is 0.03 g per kilogram of body weight, or 2.1 g for a 70 kg person.

The creatine formula

Body weight in kg × 0.03 g

In practice, a fixed daily dose of 3 to 5 g of creatine monohydrate is also commonly recommended. It gradually saturates muscle stores without a loading phase. An optional loading phase of approximately 0.3 g per kilogram for five to seven days simply speeds up this saturation.

Consistency matters more than timing. Take creatine every day with enough fluid, including on rest days.

Calculate your pre-workout caffeine dose

A dose of 3 mg of caffeine per kilogram can improve alertness, reduce perceived exertion and support certain aspects of athletic performance. For 70 kg, this is approximately 210 mg, generally consumed around one hour before exercise.

The caffeine formula

Body weight in kg × 3 mg

Start with a lower dose if you rarely consume caffeine. EFSA considers that single doses of up to approximately 200 mg and a total daily intake of up to 400 mg generally do not raise safety concerns for healthy adults.

Avoid taking caffeine late in the day if it disrupts your sleep. Also add up the caffeine from coffee, energy drinks, pre-workout supplements and any other sources consumed during the day.

Understand the omega-3 calculation

The basic calculation is 20 to 30 mg of EPA and DHA per kilogram. For 70 kg, this formula gives 1,400 to 2,100 mg per day. This is a high amount compared with the general nutritional benchmark and is not a universal requirement for athletes.

The omega-3 formula

Body weight in kg × 20 to 30 mg of EPA and DHA

For general cardiovascular health, EFSA considers approximately 250 mg of EPA and DHA per day an adequate intake for adults. Higher amounts may be studied or used in certain contexts, but they should serve a specific purpose.

Read the label carefully: 1,000 mg of fish oil does not necessarily provide 1,000 mg of EPA and DHA. Some products supply only a few hundred milligrams of these two fatty acids per capsule.

Summary of formulas for a 70 kg person

• Protein: 98 to 140 g per day based on a range of 1.4 to 2 g/kg.
• Water: approximately 2.45 L based on 35 mL/kg.
• Calorie maintenance: approximately 2,100 kcal based on 30 kcal/kg.
• Fat loss: approximately 1,540 to 1,750 kcal based on 22 to 25 kcal/kg.
• Muscle gain: approximately 2,450 to 2,800 kcal based on 35 to 40 kcal/kg.
• Creatine: 2.1 g using the 0.03 g/kg formula, or a practical dose of 3 to 5 g.
• Caffeine: approximately 210 mg based on 3 mg/kg.
• Omega-3: 1,400 to 2,100 mg of EPA and DHA based on the infographic formula.

Turn the calculations into a practical program

Knowing your nutritional benchmarks is useful, but results also depend on regular, progressive training. With FitMetrics, you can access a free catalog of exercises and workouts, complete with guided instructions and demonstration videos.

Ready-to-use workout templates help you get started quickly. You can also build your own workout and configure repetitions, durations, rest periods, supersets and other essential parameters.

The app adapts the experience to your goals, equipment, level and the muscles you want to target. Personalized statistics, performance analyses and evolving recommendations then help you measure your progress and adjust your program. Try a workout for free or start creating your own.

Precautions before applying these formulas

The calculations presented are intended primarily for healthy adults. Needs may differ during pregnancy or breastfeeding, or in cases of kidney or cardiovascular disease, medication use, an eating disorder or intensive athletic training.

In these situations, seek advice from a physician or qualified dietitian before making major changes to your diet or using supplements. A simple estimate should never replace guidance tailored to your health status.

Key takeaways

Weight-based formulas offer quick benchmarks for structuring your nutrition and supplementation. Use them to set an initial target, then adjust it based on your performance, recovery and changes in your body. The best formula is the one that supports your goal sustainably without compromising your sleep, digestion or health.