Rex says
Same equations the textbooks use — just way less awkward. Pop in your stats and I'll tell you what the number actually means for you.
Try a scenario
Click to load — tweak from there.Inputs
Result
Grams of protein per day
170
Calories from protein
680
Psst — share this and help Rex grow
One click, a permanent link with your numbers baked in.
How to use this
- 1Enter body weight (lb).
- 2Enter activity level.
- 3Read your grams of protein per day on the right — it updates as you type.
- 4Hit Share to keep the scenario or send it to someone.
About this calculator
Protein needs scale with body weight and activity level: sedentary adults need less, while strength-training or cutting individuals need more to support muscle repair and preserve lean mass in a calorie deficit. This calculator applies a protein-per-pound multiplier based on your activity level to your body weight.
Worked example
Using the values the calculator loads with:
Inputs
- Body weight: 170 lb
- Activity level: Strength training / cutting
Results
- Grams of protein per day: 170
- Calories from protein: 680
What each field means
Inputs
- Body weight (lb)
- The body weight used in the calculation, measured in lb. Starts at 170 lb so you have a working example on load. Accepted range: 50–400 lb.
- Activity level
- Pick the option that matches your situation — the maths changes per option. Choices: Sedentary, Lightly active, Active / regular exercise, Strength training / cutting.
Results
- Grams of protein per day
- Returned as a whole number and shown as the headline result. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Calories from protein
- Returned as a whole number. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
FAQ
How much protein do I need a day?
At 170 lb and a strength-training activity level (1.0 g/lb), the target is about 170 grams of protein a day, which equals 680 calories from protein.
Why does activity level change the number so much?
Sedentary people need protein mainly for maintenance (about 0.36-0.4 g/lb), while people building or preserving muscle through resistance training need more raw material for repair and growth, closer to 0.7-1.0 g/lb.
Can I eat too much protein?
For healthy kidneys, intakes up to about 1.2 g/lb are well tolerated in research; going well beyond that mostly displaces other macronutrients without added muscle benefit.
Should I use lean body mass instead of total weight?
For individuals with higher body fat percentages, using lean body mass gives a more precise target since fat tissue doesn't need protein for maintenance the way muscle does.
Accuracy and limitations
- Population formulas describe averages; individual bodies vary, especially at the extremes of height, age, or muscle mass.
- Results do not account for medical conditions, medication, or pregnancy.
- Use this as a directional reference, not a diagnosis — talk to a clinician before acting on it.
Related tools
Cite this calculator
Writing about this topic? Grab a citation — every link helps keep these tools free.
RevenueLab. (2026). How Much Protein Do I Need a Day?. Retrieved from https://www.revenuelab.fyi/toolbox/how-much-protein-do-i-need
<p>Source: <a href="https://www.revenuelab.fyi/toolbox/how-much-protein-do-i-need" target="_blank" rel="noopener">How Much Protein Do I Need a Day? — RevenueLab</a> (2026).</p>
Source: [How Much Protein Do I Need a Day? — RevenueLab](https://www.revenuelab.fyi/toolbox/how-much-protein-do-i-need) (2026).