How the calculation works
Protein needs are usually given in grams per kilogram of body weight per day. The calculator multiplies your weight by the range for your goal and rounds to the nearest gram. Weights in pounds are converted first (1 lb = 0.4536 kg).
The ranges come from widely used reference values and sports nutrition position statements, listed below. They are meant for healthy adults.
Protein ranges by goal
| Goal | g per kg | g per lb |
|---|---|---|
| General health | 0.8 | 0.36 |
| Active | 1.2 to 1.6 | 0.54 to 0.73 |
| Build muscle or strength | 1.6 to 2.2 | 0.73 to 1.00 |
| Lose fat, keep muscle | 1.8 to 2.2 | 0.82 to 1.00 |
Example: someone who weighs 70 kg and wants to build muscle aims for 70 × 1.6 = 112 g to 70 × 2.2 = 154 g of protein a day.
Where the ranges come from
- General health: 0.8 g/kg is the Recommended Dietary Allowance (RDA) for adults set by the US National Academies (Institute of Medicine). The European Food Safety Authority (EFSA) sets a similar population reference intake of 0.83 g/kg. It covers the needs of nearly all healthy adults: a minimum rather than an optimum.
- Active: The 2016 joint position of the American College of Sports Medicine, the Academy of Nutrition and Dietetics and Dietitians of Canada recommends 1.2 to 2.0 g/kg for athletes. The calculator uses the lower part, 1.2 to 1.6 g/kg, for regular exercise.
- Build muscle or strength: The International Society of Sports Nutrition (ISSN) position stand on protein and exercise (2017) gives 1.4 to 2.0 g/kg for most people who exercise. A 2018 meta-analysis in the British Journal of Sports Medicine (Morton and colleagues) found that extra protein stopped adding muscle at around 1.6 g/kg on average, with 2.2 g/kg as the upper end of its estimate.
- Lose fat, keep muscle: The ISSN position stand notes that higher intakes may help preserve lean mass while you eat fewer calories. The calculator uses 1.8 to 2.2 g/kg, towards the upper end of the ranges above.
How to use your number
- Aim to land inside your range on most days. Your weekly average matters more than any single day.
- Spread protein over the day, for example 20 to 40 g at each of three or four meals.
- Use foods you enjoy: meat, fish, eggs, dairy, tofu, tempeh, beans and lentils all count.
- If you carry a lot of body fat, your current weight can overstate your needs. A dietitian may base the target on a lower reference weight.
Related calculators
- Macro calculator: split your daily calories into grams of protein, carbs and fat.
- Calorie calculator: estimate how many calories you burn a day.
Who should not use this calculator
- People with chronic kidney disease or reduced kidney function. Protein needs are often lower and should be set by a doctor or renal dietitian.
- Pregnancy and breastfeeding, when protein needs change. Ask your midwife, doctor or a registered dietitian.
- Children and teenagers under 18. The ranges here are for adults.
- Anyone on a medically prescribed diet, or with a history of disordered eating.
