How is protein calculated?
| Situation | Grams per kg of body weight |
|---|---|
| Minimum for the average adult (RDA) | 0.8 |
| Moderate activity | 1.2–1.6 |
| Strength training or hard exercise | 1.6–2.2 |
| Losing fat while keeping muscle | 1.6–2.2 |
These come from the official dietary minimum (0.8 g/kg) and sports-nutrition research for people who exercise: the International Society of Sports Nutrition (ISSN) recommends 1.4–2.0 g/kg, and a meta-analysis by Morton et al. (2018) found that, for building muscle with resistance training, benefits level off at about 1.6 g/kg (possibly up to 2.2); intakes at the upper end are commonly advised while dieting to protect muscle. The calculator uses the middle of the range that fits your goal and activity.
What about carbs and fat?
If you enter your daily calories, the calculator sets fat at about 25–30% of calories (within the healthy 20–35% range) and gives the rest to carbohydrates. Each gram of protein or carbs = 4 kcal; each gram of fat = 9 kcal.
A worked example
Someone weighing 80 kg, moderately active, trying to lose weight, eating 2,000 kcal a day:
- Protein: 80 × 1.8 g = 144 g (576 kcal, about 29%).
- Fat: 25% of calories = 500 kcal = about 56 g.
- Carbs: the remaining 924 kcal = 231 g.
Hitting those numbers with real food
- Spread protein over 3–4 meals, for example 4 meals of about 35 g.
- Get most carbs from high-fibre foods: oats, wholemeal bread, rice, potatoes, fruit and vegetables.
- Get fat from oils, nuts, eggs and fish, in measured amounts — it is calorie-dense.
If you don’t know your daily calories, work them out first with the calorie calculator, then come back here.
Frequently Asked Questions
Is a lot of protein bad for the kidneys?
For healthy people, intakes up to about 2 g/kg are considered safe in studies. People with kidney disease must follow the amount their doctor sets, not this calculator.
Where do I get this protein from?
Chicken, meat, fish, eggs, dairy, and legumes such as beans and lentils. For example, 100 g of cooked chicken breast has about 30 g of protein, and a large egg about 6 g.
Should I split protein across meals?
It’s better spread over 3–5 meals of about 20–40 g each, rather than all at once.
Why does the calculator lower fat a little when losing weight?
It sets fat at 25% of calories for weight loss and 28% for maintenance or gain, and never below 0.6 g per kg of body weight, because the body needs a minimum of fat for hormones and vitamin absorption.
Do I have to weigh my food?
Not all the time, but weighing food for a week or two at the start teaches you portion sizes by eye, and after that you can estimate without a scale.