Protein calculator

How the calculator works

Protein advice is given in grams per kilogram of body weight, so the calculator starts there. If you enter stone and pounds it converts them first (one stone is 6.35 kg).

• Everyone gets the UK reference amount: 0.75 g of protein per kg a day. This is the Reference Nutrient Intake for adults, set to cover the needs of almost everyone in the population. For a 70 kg adult it comes to about 53 g.
• If you train regularly, it shows 1.4 to 2.0 g per kg a day, the range the International Society of Sports Nutrition (ISSN) gives for most people who exercise.
• If you are 65 or over, it uses 1.0 to 1.2 g per kg a day from the PROT-AGE expert group, or at least 1.2 g per kg if you also exercise.

How much protein should I eat in a day?

Most adults need about 0.75 g of protein per kg of body weight per day. That is the UK recommended protein intake, known as the Reference Nutrient Intake (RNI), and for a 70 kg adult it comes to about 53 g. The British Nutrition Foundation (BNF) gives 45 g a day for women and 56 g a day for men, based on body weights of 60 kg and 75 kg.

If you don't do much exercise and you're under 65, the reference amount is how much protein you need a day. Reference Nutrient Intakes are set high enough to cover the needs of about 97.5% of people, so for most it is a comfortable baseline rather than a bare minimum. Most adults already eat more than this: national survey figures quoted by the BNF put average intake at about 85 g a day for men and 67 g for women. The BNF adds that children, and women who are pregnant, need extra.

Recommended protein intake by body weight

Here is the UK reference amount of 0.75 g per kg worked out for a few common weights. The calculator does the same sum for your own weight.

The numbers are for body weight as it is. If you are carrying a lot of extra weight, a dietitian may work from a different weight; the calculator does not try to guess that.

Protein for women

The reference amount is the same 0.75 g per kg for women and men. Protein for women comes out lower in grams because the BNF's figure is based on a lower average body weight: 45 g a day for women aged 19 to 50 and 46.5 g from 50. The BNF says most women already eat more than that, at about 67 g a day. Pregnancy adds about 6 g a day. Breastfeeding adds about 11 g a day for the first six months and 8 g after that. If you are pregnant or breastfeeding, ask your midwife or GP about your diet.

How much protein to build muscle

To build or gain muscle, the ISSN puts daily protein at 1.4 to 2.0 g per kg for most people who exercise. For a 70 kg person that is about 98 to 140 g a day. It also suggests spreading protein across the day, with roughly 0.25 g per kg (about 20 to 40 g) at each meal, every three to four hours. The calculator's "per meal" line divides your daily range across three meals as a rough guide.

Protein is only part of it. The British Dietetic Association says that where muscle gain is the aim, you need resistance training and enough energy and carbohydrate overall, with protein at about 1.6 to 1.7 g per kg a day. That is roughly 112 to 119 g for a 70 kg person.

Protein after 65

Muscle tends to shrink with age, and older bodies respond less well to the same amount of protein. That is why the PROT-AGE group recommends 1.0 to 1.2 g per kg a day for healthy people over 65, at least 1.2 g per kg for those who exercise, and 1.2 to 1.5 g per kg for most older people with an acute or long-term illness.

The exception is severe kidney disease. PROT-AGE says older people with significantly reduced kidney function who are not on dialysis should not raise protein without medical advice.

How to increase your protein intake

Add a protein food to each meal and snack, rather than saving it all for one big portion. Most protein in UK diets comes from food you already eat: meat, fish, eggs, milk, yoghurt and cheese, plus beans, lentils, tofu, nuts and seeds. The BNF suggests eating a wider range of protein foods, especially beans, lentils and pulses, which are also low in fat and high in fibre, and choosing lower-fat options such as lean meat, skinless chicken, reduced-fat dairy and fish.

Because most adults already eat more than the reference amount, extra protein is mainly a question for people who train regularly or are over 65, or who have been advised to eat more by a GP or dietitian. A protein powder is a convenience, not a requirement. If you are looking at food more broadly, the fibre calculator works the same way for fibre.

Foods that give about 20 g of protein

The British Dietetic Association lists these portions, which each give approximately 20 g of protein:

• 1 small cooked chicken breast (75 g)
• 1 medium grilled fish fillet or steak (100 g)
• 1 small can of tuna or salmon (100 g)
• 3 medium eggs
• Half a 450 g pot of Greek yoghurt (225 g)
• Half a 300 g pot of low-fat cottage cheese (150 g)
• 1 large can of baked beans (400 g)
• 6½ tablespoons of Quorn mince (165 g)

A pint (600 ml) of semi-skimmed milk and two handfuls (100 g) of unsalted nuts or seeds are on the same list. One way to spread it out: eggs or Greek yoghurt at breakfast, a tin of tuna or a portion of beans at lunch, and cottage cheese or nuts as snacks.

How much protein is in a protein shake?

It depends on the product, so read the protein per serving on the nutrition table. For a powder, multiply the scoop weight by the protein per 100 g and divide by 100: a 30 g scoop of a powder with 80 g of protein per 100 g gives 24 g. Powders vary more than you might expect. A 2023 test of 47 whey supplements bought in Europe measured protein from 18% to 92% of the product, averaging 70.9% against 74.3% on the labels (González-Weller and colleagues). A glass of milk counts too, since a pint of semi-skimmed gives about 20 g. The ISSN's 20 to 40 g per meal is a useful yardstick for a single shake.

When is the best time to have a protein shake?

The best time to have a protein shake is whenever it helps you reach your daily total, because total protein matters more than the clock. A 2013 meta-analysis of randomised trials (Schoenfeld and colleagues; 20 studies on strength and 23 on muscle size) found that once other factors were accounted for, timing protein around training made no significant difference, and total daily protein was the strongest predictor of muscle gain. The ISSN says the best timing is likely a matter of individual tolerance, and suggests 20 to 40 g every three to four hours across the day.

So when to drink a protein shake is mostly about what suits your day: after training, between meals, or when a meal is hard to fit in. The British Dietetic Association adds that a healthy, balanced diet should provide enough protein to meet any increased requirements, and that supplements will not make up for poor food choices. Our guide to whey protein isolate covers the research on casein before sleep.

Who should ask first

Ask your GP or a dietitian before changing how much protein you eat if you have kidney disease, are pregnant or breastfeeding, have been told to follow a special diet, or are under 18. The numbers here are for adults.