Grams of protein per kg vs per pound

Protein targets come in two units, and most of the confusion in protein advice comes from switching between them without saying so. The conversion itself is short:

1 kg = 2.2 lb, so multiply a per-kilo figure by 0.4536 to get the per-pound one, or a per-pound figure by 2.2046 to get the per-kilo one.

Per kg of body weight	Per lb of body weight	What it is
0.8 g/kg	0.36 g/lb	The RDA: enough to avoid deficiency
1.2 g/kg	0.54 g/lb	A reasonable floor for active adults
1.6 g/kg	0.73 g/lb	Where muscle gain levels off in the research
2.2 g/kg	1.0 g/lb	Upper end of the useful range

The last row is the one worth remembering. "One gram per pound" is 2.2 g per kg. It isn't the middle of the evidence. It is the top of it.

Read your number off the table

Grams per day at both ends of the 1.6–2.2 g/kg range most people training for muscle or losing fat should be in:

Body weight	At 1.6 g/kg	At 2.2 g/kg (1 g/lb)
55 kg (121 lb)	88 g	121 g
65 kg (143 lb)	104 g	143 g
75 kg (165 lb)	120 g	165 g
85 kg (187 lb)	136 g	187 g
95 kg (209 lb)	152 g	209 g
110 kg (243 lb)	176 g	242 g

A handy check falls out of the right-hand column: at 1 g/lb, your daily grams are your weight in pounds. If a target in grams is close to your weight in pounds, it is sitting at the top of the range.

Where the units go wrong

1. "One gram per kilo" and "one gram per pound" are not the same advice

They differ by a factor of 2.2. One gram per kilo is a modest intake, a little above the RDA. One gram per pound is the high end of what is useful for building or keeping muscle. Someone who reads a per-kilo article and applies it per pound eats more than double, and someone going the other way eats less than half. Both of them believe they are following the same rule.

2. Body weight, lean mass, or goal weight

The research that produced 1.6–2.2 g/kg measured it against total body weight, in people who were mostly not carrying much fat. Scale that straight onto someone at 120 kg and you get 190–260 g a day, which is more than their muscle needs, because fat tissue doesn't need protein to maintain it.

There are two sensible fixes. One is to use lean mass, your weight minus your fat, with a correspondingly higher multiplier. The other is to use your goal weight, or a weight between your current and your goal. Both land in roughly the same place. The mistake is using a lean-mass multiplier on total weight, or a total-weight multiplier on someone with a lot of fat to lose.

3. The famous 2.3–3.1 g/kg figure

You'll often see "2.3–3.1 g per kg" quoted as the protein target for dieting athletes. The original review gave that range per kg of fat-free mass, not per kg of body weight. As the figure was repeated, the unit was dropped. Per kg of body weight, for a lean athlete, it works out to roughly 2.0–2.8 g/kg, which is very different advice for anyone with more fat than a competitive bodybuilder.

What our calculator does

The grams of protein per day calculator works from an estimate of your lean mass, then shows the result in grams per day and per kg (or per lb) of your body weight, so you can compare it with any other figure you have seen. For most people the answer lands between about 1.7 and 2.2 g per kg of body weight. It is lower for people with more fat to lose and higher for leaner people who are dieting.

Protein is the first of three budgets. Macros explained covers setting fat and carbs around it, and how much protein you actually need covers getting to the number with ordinary food.

Sophia does the conversion for you

Once the target is set, the unit stops mattering. What matters is the grams in your day, and that is what Sophia counts. You tell her what you ate in your own words. The more detail you give her, such as portions, brands and how it was cooked, the tighter her figure, but a rough description still beats leaving the meal out. She keeps your day's protein against your target, in grams, whichever unit your number started life in.