Protein
calculator

How much protein you need per day, set in grams per pound of bodyweight by goal — the ISSN research bands, not a flat percentage. On a cut it switches to lean mass, where the requirement runs higher. Imperial or metric.

How the math works

Protein needs scale with bodyweight, so the target is grams per kilogram of bodyweight, times a rate that depends on your goal. The RDA of 0.8 g/kg is the floor for sedentary adults (USDA DRI). Anyone training sits in the ISSN band of 1.4–2.2 g/kg — general active at the low end, strength and hypertrophy at the top (Jäger et al., 2017).

On a cut the anchor changes. In a deficit the job is to hold muscle while losing fat, so protein is set per kilogram of lean mass, not total bodyweight, and the band rises to 2.3–3.1 g/kg of LBM (Helms et al., 2014). Lean mass comes from your body fat percentage.

Grams per pound is the same math read the other way: the strength band of 1.6–2.2 g/kg is about 0.73–1.0 g/lb, the active band about 0.64–0.91 g/lb, and the RDA about 0.36 g/lb. The rule of thumb "a gram per pound" lands at the top of the strength band — a sensible target, not a magic number.

Worked example

A 30-year-old, 180 lb (82 kg) lifter training for size and strength. The build-muscle band is 1.6–2.2 g/kg of bodyweight:

• Low end: 0.73 g/lb × 180 lb = 131 g/day (1.6 g/kg × 82 kg)
• High end: 1.0 g/lb × 180 lb = 180 g/day (2.2 g/kg × 82 kg)
• Target range: 131–180 g/day.

Now put the same lifter in a deficit at 15% body fat. Lean mass is 82 × (1 − 0.15) = 69.7 kg — that's 154 lb. The cut band of 2.3–3.1 g/kg applies to that lean mass, not the full 180 lb:

• Low end: 2.3 g/kg × 69.7 kg = 160 g/day
• High end: 3.1 g/kg × 69.7 kg = 216 g/day

Note the direction. The cut floor of 160 g sits above the maintenance floor of 131 g for the same person. Protein goes up when calories come down.

When this calculator is wrong

Protein recommendations are too low for general health and, for muscle building, sometimes too high. The RDA of 0.8 g/kg is set to prevent deficiency in sedentary adults — it's a floor, not a training target. At the other end, the meta-regression breakpoint for muscle gain is 1.62 g/kg/day (Morton et al., 2018): past that point, more protein produced no further resistance-training gain in fat-free mass for most people. Supplement marketing rarely mentions a ceiling. The meta-analysis found one anyway.

• The counter-case is an active cut. The "too high" critique applies to maintenance and surplus. In a deficit, needs rise to 2.3–3.1 g/kg of lean mass to preserve muscle (Helms et al., 2014) — above the Morton breakpoint by design, and worth it while dieting.
• Lean-mass anchoring needs a real body fat number. The cut band is only as good as the body fat input. From a DEXA scan or careful calipers it's solid; from a bathroom scale or a guess, the error carries straight into the protein target. When body fat is unknown, use the bodyweight bands and accept a rougher number.
• Very high or very low bodyweight stretches the linear model. A flat g/kg rate assumes protein need tracks total mass. At the extremes — high body fat, or very large frames — grams per kg of lean mass is the more defensible anchor, which is why the cut path uses it.

What to do with the result

Treat the range as a floor-and-cap, not a bullseye. Landing anywhere in the band is fine; hitting the exact midpoint every day buys nothing. Set the floor as your daily minimum and spread protein across three or four meals — total intake matters far more than timing.

Then hold it steady and change other things. Protein is the macro you keep fixed while calories move for a cut or a bulk — let carbs and fat absorb the calorie change, not protein. Recompute only when your bodyweight shifts more than about 10 lb (4.5 kg), or when you switch between maintaining, building, and cutting, since the goal is what moves the band.

Common questions

How much protein do I need per day?

It depends on what you're doing. Sedentary: the RDA of 0.8 g/kg (about 0.36 g/lb). Training: the ISSN band of 1.4–2.2 g/kg (about 0.64–1.0 g/lb), with strength and hypertrophy at the top. On a cut: 2.3–3.1 g/kg of lean mass to hold muscle in the deficit (Helms et al., 2014).

Is it grams per pound of bodyweight or lean mass?

Bodyweight for general, active, and muscle-building goals — that's how the ISSN band is expressed. Lean mass on a cut, where preserving muscle is the point and the Helms band is written per kilogram of lean tissue. For someone at a typical body fat the two are close; for the very lean or very heavy, lean mass is the more honest anchor.

Do I need more protein when cutting?

Yes — the band rises in a deficit, it doesn't fall. For the 180 lb (82 kg) reference lifter, the maintenance floor is 131 g/day but the cut floor is 160 g/day. Lower calories raise the risk of losing muscle alongside fat, and higher protein is the main defence against that (Helms et al., 2014).

Can you eat too much protein?

For building muscle, there's a point of diminishing returns: past about 1.62 g/kg/day the evidence shows no further gain in muscle mass for most trained adults (Morton et al., 2018). Eating more isn't harmful for healthy kidneys — it just doesn't add muscle. The exception is an active cut, where the higher lean-mass band is doing a different job.

How much protein to build muscle?

The ISSN strength band of 1.6–2.2 g/kg (about 0.73–1.0 g/lb) covers it, and the Morton breakpoint says there's little reason to go past roughly 1.6 g/kg for hypertrophy. For the 180 lb reference lifter that's 131–180 g/day. Total daily intake and training drive the result; the exact meal-by-meal split matters much less.

Is 0.8 g/kg enough if I lift?

No. The RDA was set to prevent deficiency in people who don't train, and it's roughly half the muscle-building target. If you lift, start at the ISSN band of 1.4–2.2 g/kg and treat 0.8 g/kg as the floor you never want to be under, not a goal.