Free tool
Protein calculator
Protein is the one macro worth a gram target. Set it from body weight, check it still sits inside the published energy range, then stop chasing the other two.
Updated 2026-08-16By Chris RichardsAll tools
Your estimate
g protein / day · 512 kcal from protein
Estimate only — verify with a weight log over 2–3 weeks. Not medical advice.
How the number is calculated
This tool multiplies body weight in kilograms by a grams-per-kilo choice. The Dietary Reference Intakes set the adult RDA at 0.8 g/kg — a floor against deficiency, not an optimum for training. The Acceptable Macronutrient Distribution Range allows protein from 10% to 35% of energy.
People lifting and eating in a deficit commonly sit around 1.6–2.2 g/kg, which still fits that energy band for most calorie targets. Past that, extra protein is mostly extra calories.
A worked example
80 kg at 1.6 g/kg is 128 g, or 512 kcal. On a 2,200-calorie day that is 23% of energy — inside 10–35%. The same 128 g on a 1,600-calorie day is 32%: still inside, and a reason not to push grams higher just because the cut feels virtuous.
When a percentage is the wrong tool
A 30% protein target on a very low calorie budget can undershoot grams. A 30% target on a large budget can overshoot usefulness. Grams per kilogram keeps the floor attached to the body, not to an arbitrary calorie total. The macro calculator will split whatever calories remain after protein.
If you are already eating well above 2.2 g/kg, this tool will not invent a reason to go higher. Extra protein is food. It still counts. Put the rest of the budget into meals you will actually cook.
The mistake people make
Hitting protein by drinking it at 10pm to close a 12 g gap. That is worse than the gap. Within about 10 g is close enough for food-label arithmetic. Clinical kidney or liver advice belongs with a clinician, not this page.
The other mistake is copying a 200 g target from someone twice your size. Grams per kilogram exists so the number moves with the body. Recalculate after a large weight change. If you are in a surplus, you still do not need to chase the top of the AMDR for its own sake.
FAQ
Should I use lean mass instead of body weight?
Only if you have a real composition measurement. Most people do not. Body weight is the input the RDA uses. If you are carrying a lot of fat mass, some coaches use an adjusted weight — that is a coaching choice, not a DRI rule.
Is more protein always better in a deficit?
Up to a point it helps fullness and lean-mass retention. It does not create the deficit. Calories still decide the direction of the scale.
Do I need to hit this every day?
Most days. A weekly average that lands near the target is the adult version of the habit.
Does this include plant protein?
The gram target does not care where the grams come from. Variety and total energy still matter. This calculator will not plan a vegan menu.
Should I eat protein at every meal?
Spreading it is easier for most people. The daily gram total is the number this tool cares about. Meal timing is a preference, not a DRI rule.
Sources
- [1] Acceptable Macronutrient Distribution Range (protein 10–35% of energy; RDA 0.8 g/kg) — National Academies of Sciences, Engineering, and Medicine — Dietary Reference Intakes
- [2] Mifflin MD, St Jeor ST, et al. “A new predictive equation for resting energy expenditure in healthy individuals” (1990) — American Journal of Clinical Nutrition 51:241–247
General nutrition information, not medical advice. Calorie and macro targets are estimates — talk to a doctor or a registered dietitian before changing your diet, especially if you are pregnant, managing a health condition, or have a history of disordered eating.
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