Protein is the macronutrient with the clearest evidence behind its targets and the largest effect on body composition. This calculator scales your intake to body weight and to what you are actually asking your body to do — the two things generic advice ignores.
- RDA minimum
- 0.8 g per kg of body weight
- Building muscle
- 1.6–2.2 g per kg
- Losing fat while training
- 1.6–2.4 g per kg
- Adults over 65
- At least 1.0–1.2 g per kg
- Per-meal ceiling
- About 0.4 g per kg per feeding
Formula
ISSN and Morton et al. meta-analysis rangesDaily protein (g) = body weight (kg) × target g/kg
- body weight
- — Total body weight in kilograms
- target g/kg
- — 0.8 sedentary · 1.2–1.6 active · 1.6–2.2 building muscle · 1.6–2.4 in a deficit
Targets are set against total body weight here. At very high body-fat percentages, scaling to lean body mass instead avoids overestimating — the difference is negligible for most people.
Protein Intake Calculator examples
| Input | Result | Category |
|---|---|---|
| 150 lb, general activity | 95 g/day | General health and activity |
| 150 lb, building muscle | 129 g/day | Building muscle |
| 180 lb, building muscle | 155 g/day | Building muscle |
| 180 lb, cutting | 163 g/day | Losing fat while training |
| 200 lb, sedentary | 82 g/day | Sedentary |
| 140 lb, age 70 | 89 g/day | General health and activity |
Why the RDA is not a target
The recommended dietary allowance of 0.8 g/kg is defined as the amount that meets the needs of 97.5% of healthy adults — meaning the amount at which nitrogen balance is not negative. It is a deficiency threshold.
It says nothing about the intake that best supports muscle retention, satiety, or recovery from training. Those questions have been studied separately, and the answers land consistently higher: roughly double the RDA for anyone training seriously.
How much protein to build muscle
The 2018 Morton meta-analysis of 49 trials found gains in lean mass increased with protein intake up to about 1.6 g/kg, with a plausible upper bound around 2.2 g/kg once individual variation is accounted for. Above that, no further benefit was detectable.
That is the basis for the range shown. Going substantially higher is not harmful for people with healthy kidneys, but it displaces calories that would be more useful as carbohydrate or fat.
Protein when losing weight
This is the situation with the highest requirement, which surprises people who assume protein is only for bulking.
- In a calorie deficit the body will break down muscle for fuel unless dietary protein and a training stimulus give it a reason not to.
- Protein has the highest thermic effect of the three macros — roughly 20–30% of its calories are spent digesting it, against 5–10% for carbohydrate and 0–3% for fat.
- It is the most satiating macro per calorie, which makes the deficit itself easier to hold.
The leaner you already are and the steeper the deficit, the closer to the top of the range you should sit.
Does timing matter?
Far less than total daily intake, but not nothing. Muscle protein synthesis appears to saturate at roughly 0.4 g/kg in a single feeding, so spreading intake across three or four meals uses it more efficiently than one large serving.
The 'anabolic window' — the belief that protein must be consumed within an hour of training — has not held up. Total daily intake dominates, and meal timing produces small effects at best.
Is high protein bad for your kidneys?
In people with healthy kidneys, no. Controlled trials at intakes well above 2 g/kg, some running for years, have found no adverse effect on kidney function.
Frequently asked questions
How much protein do I need per day?
Between 1.2 and 1.6 grams per kilogram of body weight for general health, rising to 1.6–2.2 g/kg if you are training to build muscle. For a 150 lb person that is roughly 82–110 g for general health and 110–150 g for muscle building.
Is 100 grams of protein a day enough?
It depends on your weight and goal. For a 150 lb person aiming for general health, 100 g is comfortably adequate. For the same person trying to build muscle or losing fat while training, it sits at the low end of the useful range.
Can your body only absorb 30 grams of protein at a time?
No — absorption is near complete regardless of dose. What saturates is muscle protein synthesis, at roughly 0.4 g/kg per meal. Excess protein is still used, just for other purposes, so a large serving is not wasted.
Do older adults need more protein?
Yes. Muscle becomes less responsive to protein with age, so guidelines recommend at least 1.0–1.2 g/kg after 65, and higher during illness or recovery. This calculator raises the floor automatically for ages 65 and over.
Should I count protein by total or lean body weight?
Total body weight works for most people and is what this calculator uses. At very high body-fat percentages it overestimates somewhat, so scaling to lean mass or to a goal weight is more accurate in that case.
Is too much protein harmful?
Not for people with healthy kidneys. Trials at intakes above 2 g/kg have found no harm to kidney function. The practical limit is that protein displaces other calories rather than any toxicity.
Sources
- A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength — Morton et al., British Journal of Sports Medicine, 2018
- International Society of Sports Nutrition Position Stand: protein and exercise — Jäger et al., Journal of the International Society of Sports Nutrition, 2017
- Evidence-based recommendations for optimal dietary protein intake in older people (PROT-AGE Study Group) — Bauer et al., Journal of the American Medical Directors Association, 2013
- Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids — Institute of Medicine, National Academies Press, 2005