How Much Protein Per Day: RDA vs. Deficit Targets

The figure most people have seen is 0.8 grams of protein per kilogram of body weight per day. That number is the Recommended Dietary Allowance (RDA), set by the Institute of Medicine in 2005. It is the average daily intake sufficient to meet the protein needs of nearly all (97–98%) healthy sedentary adults. It is not a target for muscle retention during weight loss, and it is not a target for building muscle. The RDA is a floor, not an optimum. This page works in grams per kilogram because a protein figure in grams alone says nothing without the person it belongs to.

The RDA: a minimum, not a goal

The RDA of 0.8 g/kg comes from nitrogen-balance studies. Those studies measure how much protein is needed to replace the protein the body loses each day. The figure is adjusted upward to cover the variability between people. For a 70 kg adult, 0.8 g/kg is 56 grams per day. For a 60 kg adult, it is 48 grams. The RDA is set to prevent deficiency, not to support muscle growth or preserve lean mass when calories are restricted. A 2014 review by Phillips and Van Loon in the Journal of Sports Sciences notes that the RDA is inadequate for athletes and for people in an energy deficit. The RDA is a starting point, not an endpoint.

Protein for muscle retention in a deficit

When calories are reduced, the body can break down muscle for energy. Higher protein intake helps preserve lean mass. A 2014 meta-analysis by Helms et al. in the Journal of the International Society of Sports Nutrition reviewed the literature on protein intake during energy restriction. The evidence clusters at 1.6 to 2.2 grams per kilogram of body weight per day. The upper end of that range matters most when the deficit is large (more than 500 kcal per day below maintenance) or when the person is already lean. For a 70 kg person, that range is 112 to 154 grams per day. For a 60 kg person, it is 96 to 132 grams per day. The exact figure within that range is not settled by the evidence; the range itself is the finding.

How much protein to build muscle

For muscle gain, the evidence is slightly different. A 2017 meta-analysis by Morton et al. in the British Journal of Sports Medicine found that protein intake beyond 1.6 g/kg per day did not further increase muscle mass in resistance-trained individuals. That analysis included 49 studies and over 1,800 participants. The confidence interval extended to 2.2 g/kg, so the true value could be higher for some people. A 2018 review by Witard et al. in Sports Medicine suggests that 1.6 g/kg is sufficient for most, but individual variation exists. For a 70 kg person, 1.6 g/kg is 112 grams per day. For a 60 kg person, it is 96 grams per day. The evidence stops being clear above 1.6 g/kg for muscle gain; the upper bound is not established.

Worked calculation: protein per day for a 70 kg adult

This calculation uses the Mifflin-St Jeor equation for maintenance calories, then applies protein targets. The Mifflin-St Jeor equation is:

For men:   BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age in years) + 5
For women: BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age in years) − 161

Example: a 70 kg, 175 cm, 30-year-old man.

BMR = (10 × 70) + (6.25 × 175) − (5 × 30) + 5
BMR = 700 + 1093.75 − 150 + 5
BMR = 1648.75 kcal/day

Apply an activity multiplier. For a sedentary lifestyle, multiply by 1.2.

Maintenance = 1648.75 × 1.2 = 1978.5 kcal/day

Mifflin-St Jeor has a standard error of about 10% for predicting maintenance calories. So the true maintenance for this person is likely between 1780 and 2176 kcal/day. That uncertainty matters when setting a deficit.

Now protein. The RDA is 0.8 g/kg:

RDA protein = 0.8 × 70 = 56 g/day

For muscle retention in a deficit, use 1.6 to 2.2 g/kg:

Lower bound = 1.6 × 70 = 112 g/day
Upper bound = 2.2 × 70 = 154 g/day

If this person eats 112 grams of protein per day, that is 448 kcal from protein (112 × 4 kcal/g, using Atwater factors). If they eat 154 grams, that is 616 kcal from protein. The rest of the diet comes from fat and carbohydrate. The protein target is not a percentage of calories; it is a fixed amount based on body weight.

Table: protein targets by condition

What people get wrong about protein

The most common mistake is treating the RDA as a target. The RDA is set to prevent deficiency, not to optimize body composition. A second mistake is using a percentage of calories for protein. If calories are reduced, a percentage-based protein target falls, which is the opposite of what is needed to preserve muscle. A third mistake is assuming more protein is always better. The evidence shows a plateau around 1.6 g/kg for muscle gain and 2.2 g/kg for muscle retention in a deficit. Above those levels, the additional protein is oxidized for energy or excreted. The mistake is natural because public health messaging simplifies the RDA into a single number, and because protein is often discussed in grams rather than grams per kilogram.

Where the evidence stops being clear

The exact optimal protein intake within the 1.6–2.2 g/kg range is not settled. Individual variation in protein requirements is not well quantified. The interaction between protein intake and resistance training volume is not fully understood. The long-term effects of high protein intake on kidney function in healthy adults are not a concern in the literature, but the evidence for very high intakes (above 3 g/kg) is limited. For people with kidney disease, protein intake should be discussed with a clinician. This page does not provide medical advice. If you have or suspect an eating disorder, contact the National Eating Disorders Association (NEDA) Helpline at 1-800-931-2237.

FAQ

Q: How much protein per day do I need to build muscle? A: The evidence clusters at 1.6 grams per kilogram of body weight per day for muscle gain. A 2017 meta-analysis by Morton et al. found no further benefit above that level, though the confidence interval extends to 2.2 g/kg. For a 70 kg person, that is 112 grams per day.

Q: Is 0.8 g/kg of protein enough? A: 0.8 g/kg is the RDA, the minimum to prevent deficiency in sedentary adults. It is not enough for muscle retention during weight loss or for muscle gain. For those goals, 1.6–2.2 g/kg is the evidence-based range.

Q: Can I eat too much protein? A: For healthy adults, high protein intake is not associated with kidney damage in the literature. However, protein beyond what the body can use is oxidized for energy. The plateau for muscle gain is around 1.6 g/kg, and for muscle retention in a deficit, around 2.2 g/kg.

Q: How do I calculate protein per day? A: Multiply your body weight in kilograms by the target in g/kg. For a 70 kg person using 1.6 g/kg: 70 × 1.6 = 112 grams per day. Use the RDA of 0.8 g/kg only as a minimum.

Q: Does protein source matter? A: Total daily protein intake is the primary driver. Animal and plant sources can both meet needs, though plant proteins may be slightly less digestible. A 2019 review by Mariotti and Gardner in The Lancet Planetary Health notes that protein quality varies, but total intake matters most for most people.