Protein calculator for weight loss

How much protein do you actually need to lose weight?

Most protein calculator weight loss tools spit out one number with no explanation. The research behind the number matters, so here’s the short version: for most adults trying to lose weight, the evidence-backed range is 1.2–1.6 g of protein per kg body weight per day, with at least 25–30 g at each main meal¹. That’s higher than the baseline 0.8 g/kg most public-health guidelines quote — because those numbers are designed to prevent deficiency, not to help you preserve muscle while eating less.

For someone who weighs 72 kg, that comes out to 86–115 g per day. That sounds like a lot until you realise it’s a chicken breast, a tub of Greek yoghurt, two eggs and a handful of lentils across your day. The calculator above lands on the specific number inside that range based on how active you are and whether you’re training for muscle.

Before we get into the why, one myth to retire: higher-protein diets do not damage healthy kidneys. A 2018 systematic review found no difference in kidney function between healthy adults eating higher- versus normal-protein diets⁴. That’s worth knowing if “you’ll wreck your kidneys” has been bouncing around in the back of your head.

Why protein matters more in a deficit

When you eat below maintenance, your body loses weight. The goal is to make sure most of what it loses is fat, not muscle. Protein does three specific jobs that make that happen.

1. It preserves muscle mass. In a deficit, the body breaks down muscle tissue to access amino acids it can’t produce on its own. Eating enough protein signals that those amino acids are coming in via food, so muscle isn’t the first thing on the chopping block. The protein intake threshold to preserve muscle during weight loss sits right around the 1.2–1.6 g/kg range the calculator uses¹.

2. It costs more calories to digest. The thermic effect of food — calories your body spends breaking down what you eat — is roughly 20–30% of the calories in protein, compared to 5–10% for carbohydrates and 0–3% for fat. Eat 100 g of protein (400 kcal) and your body spends 80–120 kcal just processing it.

3. It makes you less hungry. Gram for gram, protein is the most satiating macronutrient. Meals built around protein lower subsequent calorie intake more than matched meals built around carbs or fat. In practice, this means the “white knuckle” hunger that ends most diets gets a lot easier to manage.

How the calculator picks your number

The calculator multiplies your body weight by a grams-per-kg figure that moves with your activity level and goal. The table is:

Weight loss
  Sedentary         1.2 g/kg
  Lightly active    1.4 g/kg
  Moderately active 1.6 g/kg
  Very active       1.8 g/kg
  Extra active      2.0 g/kg

Muscle gain (resistance training)
  1.6–2.2 g/kg depending on activity

The weight-loss column anchors on Leidy 2015¹ (1.2–1.6 g/kg with 25–30 g per meal). For how much protein to build muscle, the column follows Morton 2018’s meta-analysis of 49 trials, which found protein supplementation stops adding to resistance-training gains above ~1.6 g/kg³. The higher 2.0–2.2 g/kg ceiling comes from Helms 2014, which argues for higher intakes specifically for lean, resistance-trained athletes in a deficit². For most people, sitting in the 1.6–1.8 range is plenty.

Protein by age, sex and training status

The calculator’s default range suits most adults. A few populations benefit from sitting at the higher end of the range.

Women over 50. One of the most-searched phrases around this topic is “protein intake for weight loss female”, and the specific answer is this: protein needs become genuinely more important after menopause. Anabolic resistance — the muscle’s reduced response to a given dose of protein — increases with age, so meals need more protein to trigger the same muscle-protein-synthesis response. For women over 50 losing weight, aim for 1.4–1.8 g/kg rather than the lower end of the range.

Resistance-trained athletes in a deficit. If you lift 3+ times a week and you’re already relatively lean (under ~22% body fat for women, ~15% for men), the Helms review supports going up to 2.3–3.1 g/kg of fat-free mass — typically 2.0–2.2 g/kg of total body weight². This is the ceiling the calculator tops out at under “very active / muscle gain.”

Endurance athletes. Runners, cyclists and triathletes need slightly more than the sedentary baseline but less than lifters — 1.4–1.6 g/kg covers most of the training volume seen in recreational endurance sport.

10 protein sources that make hitting your target easy

These are the foods that do the most work per mouthful. The result column above picks three based on your dietary preference — below is the full shortlist, grouped.

Omnivore (high density, low fuss)

• Chicken breast — 30 g protein per 100 g cooked. The anchor food in most high-protein diets for a reason.
• Greek yoghurt (0% fat) — 10 g per 100 g. A 170 g tub gets you 17 g; pair with berries for breakfast and you’re already a third of the way there.
• Tinned tuna — 26 g per 100 g can. Cheap, portable, zero prep.
• Eggs — 6 g per large egg. Surprisingly not the highest-density option, but the amino-acid profile is excellent.

Vegetarian

• Cottage cheese — 11 g per 100 g. Often overlooked; low calorie density makes it ideal for a deficit.
• Firm tofu — 17 g per 150 g. The single highest-density plant protein by far.
• Lentils — 13 g per 150 g cooked. Cheap, fills you up, adds fibre.

Vegan

• Tempeh — 20 g per 100 g. The densest whole-food vegan protein source.
• Chickpeas — 13 g per 150 g cooked. Interchangeable with lentils.
• Pea protein powder — 24 g per 30 g scoop. Yes, powder counts. It’s just concentrated, minimally-processed protein.

If you’re building meals around these, our high-protein breakfasts and vegan high-protein dinners are good starting points.

Can you eat too much protein?

The calculator above doubles as a high protein diet calculator when you set the goal to “muscle gain” with a very-active level — targets go up to around 2.2 g/kg. That’s high enough that the classic concerns about a high-protein diet come up. The short answer is: probably not in any way that matters for healthy adults. The three concerns that come up most often:

Kidneys. The 2018 Devries systematic review looked at 28 studies on higher-protein diets and kidney function and found no meaningful difference in healthy adults, even at intakes above 2.0 g/kg⁴. If you have existing chronic kidney disease, that’s a different conversation with your GP.

Bone density. Earlier concerns that high-protein diets leach calcium from bone have been reversed in the more recent literature — higher protein intake actually correlates with better bone-mineral density in older adults, likely because muscle mass and bone density are linked.

Cost and convenience. This is the practical limit. Hitting 150+ g per day from animal sources gets expensive; from exclusively whole plant sources it takes some planning. The calorie calculator pairs naturally with this one — once you know your calorie target, allocating 25–30% of it to protein tends to land you right in the optimal grams-per-kg range without a spreadsheet.

Prefer not to think about it? The high-protein weight-loss guide on the blog walks through what a week of meals actually looks like at 1.6 g/kg — and the Nutriguide quiz below will build you a plan in 2 minutes that hits the number automatically.