The GLP-1 protein calculator
sized to fat-free mass
Protein Calculator: Supporting Muscle Preservation on GLP-1s
Note: we strongly recommend setting your protein goal based on a measurement of your body fat % today, using the Smart or Advanced tabs above. A DEXA scan is the most accurate, and a smart scale is much better than nothing. Lacking that, we estimate your current body fat to be 27% ±5%, based on height, current weight, age and sex with our DEXA-calibrated algorithm.
YOUR DAILY PROTEIN TARGET
160g/day
Disclaimer: This calculator provides a general nutrition target, not a prescription. It is not intended for people with kidney disease or other conditions that limit protein intake. With kidney disease, providers often advise eating less protein, not more. Talk to your provider before changing your protein intake.
IN SUMMARY
The calculator above runs the exact rule the Bild Health app ships: 2.4 g of protein per kilogram of fat-free mass per day in fat loss mode, 2 in maintaining mode, never below 80 g for men or 60 g for women. What makes it different is the denominator. Every other GLP-1 protein calculator divides by body weight, a number that shrinks as the diet works. Fat-free mass is the tissue protein actually feeds. In the app, the same rule recalculates automatically as your measured lean mass moves.
The method, shown
Three choices define the rule. Why fat-free mass? Because body-weight formulas shrink your target as the scale falls. Lose forty pounds and a per-pound formula feeds forty pounds less of you, but the muscle that needs feeding shrank by far less than forty pounds' worth. Why 2.4? It comes from the one widely used protein guideline written on fat-free mass. That range is 2.3 to 3.1 g/kg, written for lean, hard-training athletes mid-diet. We sit at the bottom on purpose: a GLP-1 user is less lean and less trained than those athletes, and eating past the level that holds muscle buys nothing. Why floors? Because protein need does not shrink all the way down with a shrinking body. Below 80 g for men or 60 g for women, the engine ignores the formula. The full reasoning is in the published methodology, and the evidence for dividing by fat-free mass at all is on The Science.
Two habits the tool cannot do for you. Spread the grams out: in a small crossover study of eight adults, the same daily protein built muscle protein about 25% faster spread across meals than crowded into dinner, and a suppressed morning appetite pushes everything toward dinner. And log what you actually eat. On these medications, the gap between planned protein and eaten protein grows quietly. That is why the app charts intake against the target instead of trusting the plan.
From daily target to plate
The math is the easy part: split the day's target per meal across the meals that actually happen, protein first each time. Dense sources when volume is hard. Something liquid on the flat days after a shot. The hard part is noticing when you are short: an appetite that fills early makes under-eating feel like being done, not like falling behind. In the app, protein is one tap on the Today screen: today's meter there, the week's columns on the Week screen, both against a target the app computes from your own body-composition scale readings. The target re-sizes itself as your measured fat-free mass changes. The number feeds the full keep-the-muscle plan, and the same engine's hydration rule has its own calculator.
Where these numbers come from
- 01
International Journal of Sport Nutrition and Exercise Metabolism · 2014 · Helms ER, et al. Int J Sport Nutr Exerc Metab. 2014;24(2):127–138
- 02
The FASEB Journal · 2013 · Pasiakos SM, et al. FASEB J. 2013;27(9):3837–3847
- 03
Dietary protein distribution positively influences 24-h muscle protein synthesis
The Journal of Nutrition · 2014 · Mamerow MM, et al. J Nutr. 2014;144(6):876–880
- 04
A six-constant estimator of fat-free mass from height, weight, age and sex, fit to NHANES whole-body DEXA
Bild Health · 2026 · Bild Health methods paper, 2026. In preparation; constants and evaluation on file
The GLP-1 protein calculator, answered
How much protein do I need on a GLP-1?
Bild Health's engine computes 2.4 g per kilogram of fat-free mass per day in fat loss mode and 2 in maintaining mode, with absolute floors of 80 g for men and 60 g for women. Enter your numbers above and the calculator runs that exact rule. The output is a target to eat toward, not a prescription.
Why fat-free mass instead of body weight?
Because body weight is the wrong number for a body that is changing. A per-body-weight formula shrinks your target as the diet works: it tracks the fat you lost, not the muscle you are feeding. Size the target to fat-free mass and it stays attached to what it protects.
What if I don't know my fat-free mass?
Use the tabs. Basic estimates it from your height, weight, age and sex, with our own formula fit to 5,020 DEXA scans from the national health survey. That estimate is good to ±5 points four times in five, so a measurement always beats it. Smart uses the body-fat percentage off your body-composition scale. Advanced takes the percentage off a DEXA report. Each tab swaps a guess for a measurement, and the app keeps the number current from that scale.
Does my protein target change over time?
Yes, twice over. The coefficient is 2.4 in fat loss mode and 2 in maintaining mode, because maintenance needs less than a deficit does. Which mode you are in is yours to set, and the app asks you to switch once your measured body fat has held at your goal for a week. And the fat-free mass underneath the math changes too. The app re-runs the rule from your newest measured lean mass and restates the number only when it has moved enough to matter.
Is more protein always better in a deficit?
No. In the trial this page cites, doubling the reference intake held on to more fat-free mass, and tripling it added nothing further. Hit the target consistently, spread it across the day, and stop there.
Related pages
- How to Keep MuscleOzempic Muscle Loss: How to Keep Muscle on a GLP-1
- For MenGLP-1 Muscle Loss in Men: Keeping Muscle After 40
- For WomenGLP-1 Muscle Loss in Women: Menopause, Muscle and Bone
- Water CalculatorHow Much Water Per Day on a GLP-1
- Protein EstimatorProtein Estimator: Protein in a Meal From a Photo
- Muscle Loss CalculatorGLP-1 Muscle Loss Calculator
The calculator is the rule. The app is the loop.
Bild Health keeps fat mass, lean mass, protein, training and your dose history in one record. The lean number is measured from your scale, anchored by imported DEXA scans.
Lose the fat. Keep the muscle.