Protein Calculator

How a protein calculator works

Every protein calculator does the same short sum. Pick a range in grams of protein per kilogram of body weight, multiply by your weight, and you’ve got a daily range in grams. The hard part is choosing the range, and that’s where most calculators quietly bury a judgment call. We’d rather show you ours.

This protein calculator gives you a range instead of a single number, plus an “aim for” figure at the midpoint, rounded to the nearest 5 g. Anywhere inside the range is defensible. The midpoint is just a convenient place to start.

See the bits marked as our judgment? You’d want to know which numbers came from a paper and which came from us.

Here’s how it plays out for an 80 kg lifter who wants to build muscle. A range of 1.6 to 2.2 g per kg is 128 to 176 g a day. The midpoint, rounded, is 150 g. Over four meals that’s about 38 g each, right inside the ISSN’s 20 to 40 g guide. Don’t expect every day to land exactly there. Close enough, most days, is the whole game.

Why you see 1.6 and 2.2 everywhere

Both trace back to one 2018 meta-analysis. Morton and colleagues pooled 49 trials and 1,863 people who trained with weights for at least six weeks, then asked how much protein it took before extra protein stopped adding muscle. The breakpoint landed at 1.62 g per kg a day. The confidence interval around it was wide, reaching about 2.2 g per kg, which is why 1.6 to 2.2 became the standard range. Two other findings matter. Extra protein helped more in people with training experience, and less as people got older.

It’s an estimate of where gains level off, not a hard ceiling, and it came from trials where people added protein supplements. Treat it as a good place to aim. Don’t treat it as a line you fall off.

Protein while cutting

Dieting changes the picture. In a 2016 trial, 40 young men ate about 40% below their energy needs for four weeks while training six days a week. The group on 2.4 g per kg gained about 1.2 kg of lean mass and lost 4.8 kg of fat. The group on 1.2 g per kg gained about 0.1 kg of lean mass and lost 3.5 kg. Higher protein won on both counts.

Take that with some salt. It lasted four weeks, it was in young men, the training load was brutal, and one author disclosed funding from dairy industry groups. For lean, trained athletes cutting hard, a 2014 review of six studies put the need higher still, at 2.3 to 3.1 g per kg of lean mass, scaled up with the severity of the diet and how lean you already are. That’s a specialist range. If you enter your body fat % above and pick the cutting goal, the protein calculator shows it, so you can see the gap between a sensible default and what a lean competitor might do.

To pair this with calories, our reverse TDEE calculator finds your real maintenance, and the body fat percentage calculator gives you the number the lean-mass view needs.

How to split it across meals

The ISSN position stand suggests 0.25 g per kg per serving, or an absolute 20 to 40 g, spread every three to four hours. For an 80 kg person that’s 20 g. Honestly, the evidence on timing is mixed. A 2014 review of natural bodybuilding preparation found that changes in timing and frequency had little effect on fat loss or lean mass retention. Our reading: get the daily total right first, then fit the meals around your life.

What about the RDA?

The RDA of 0.8 g per kg is the amount that keeps most healthy adults from becoming deficient. It isn’t a performance target. The ISSN position stand puts most exercising people at 1.4 to 2.0 g per kg, well above it, which is why every goal here except general health starts higher. For adults over 65, the PROT-AGE group recommends at least 1.0 to 1.2 g per kg, and 1.2 to 1.5 for people with acute or chronic illness.

Where this protein calculator falls short

Three limits. It works from body weight, so if you carry a lot of extra fat a per-kilo number can run high, which is why the body fat option exists. It ignores protein quality and the rest of your diet. And it assumes you’re a healthy adult. If you have kidney disease or another condition that affects protein, your doctor’s advice beats any calculator, this one included.