Macro Calculator for Weight Loss

How this fat-loss macro calculator works

This page runs one locked calculation: your maintenance calories, minus a steady deficit, split protein-first. The math is shown in full below, so you can verify every number the tool gives you:

Check the math: a worked example

Take a 30-year-old man, 75 kg, 172 cm, lightly active. Here is every step, with nothing hidden:

Run the same inputs through the calculator above and you will get the same numbers. That is the point: a tool you can audit is a tool you can trust.

Why fat-loss macros are different

Losing fat and losing weight are not the same project. The scale cannot tell the difference between a kilo of fat and a kilo of muscle, but your knees can. This calculator is tuned for one specific job: a moderate deficit that takes fat off while leaving muscle alone.

The deficit is set at 500 kcal below maintenance, which works out to roughly half a kilo per week for most people. That pace is deliberate. Push the deficit to 1,000 kcal and weight drops faster, but a bigger share of it is muscle, and muscle is slow and expensive to rebuild.

Protein is where this page differs most from a generic calculator. In a surplus the body holds onto muscle easily; in a deficit it starts looking for tissue to burn, and muscle is on the list. Setting protein at 2.0 g per kg per day is the nutritional equivalent of telling your body the muscle is not available for fuel. Fat stays near 25% of calories to keep hormones steady, and carbohydrates take whatever is left, which is usually enough to keep training quality up.

The muscle you keep is joint protection

Here is the part most diet advice skips, and the reason a physiotherapist wrote this page. Muscle is not decoration. It is the active support system for every joint you own: quadriceps that unload the knee, glutes and core that protect the lower back, rotator cuff muscles that keep the shoulder tracking properly.

Crash dieting tears that system down along with the fat. Research on knee osteoarthritis found that each pound of body weight lost takes about four pounds of pressure off the knee with every step, which is a genuine argument for losing fat. But the reverse is equally true: the muscle you lose in an aggressive diet no longer absorbs force, so your joints take more of it. People who diet hard and train little often arrive at their goal weight with achier knees and a weaker back than when they started.

The fix is unglamorous: lose the fat slowly, keep protein high, and keep resistance training in your week. The number on the scale matters less than what the remaining weight is made of.

Protein at every meal, not just over the day

The calculator gives you a daily protein target and a per-meal table for a reason. Muscle repair runs in pulses: each protein-containing meal triggers a few hours of muscle building, and the effect tops out around 30 to 40 grams per meal for most people.

That is why 150 grams of protein split across four meals beats the same 150 grams eaten mostly at dinner. The default of four meals a day is not a rule, it is a practical rhythm: breakfast, lunch, a post-training meal and dinner, each anchored by a palm-and-a-half sized portion of meat, fish, eggs, dairy or lentils.

If you prefer three bigger meals, the math still works; just make each one count. What does not work is grazing on carbs all day and hoping one protein-heavy dinner covers it. It will not.

When fat loss stalls, do this first

Two or three weeks with no movement on the scale is normal, not a failure. Before you cut calories further, run this checklist.

First, recalculate. You are lighter than when you started, so your maintenance calories are lower too. The intake that created a deficit at 85 kg is maintenance at 78 kg. Run your new numbers through the calculator above.

Second, audit adherence honestly. Most stalls are not metabolic mysteries; they are weekends. Two untracked days can erase five careful ones. Track everything for one full week, including oils, sauces and the handfuls, before deciding the plan is broken.

Third, check sleep and steps. Short sleep raises hunger and tanks training quality; a low daily step count quietly removes hundreds of calories of expenditure.

Only after all three check out should you deepen the deficit, and only by 100 to 200 kcal, or take a short diet break: one to two weeks at maintenance to recover adherence and training drive. Never crash below the floor warning shown on this page.

Mistakes that cost you muscle

1. A deficit that is too aggressive. Beyond about 750 kcal a day, muscle loss accelerates and training falls apart. The extra speed is not worth it.

2. Protein set too low. Anything under about 1.6 g/kg during a cut is gambling with muscle. This calculator will not let you make that mistake by default.

3. Cutting carbs to zero. Very low carb intakes flatten training sessions, and flat sessions do not preserve muscle. Keep enough carbs to train hard.

4. Cardio only, no lifting. Steady cardio burns calories, but only resistance training tells the body to keep muscle while dieting. Two to four lifting sessions a week is the minimum effective dose.

5. Never recalculating. Your targets have a shelf life of about a month. Re-run the numbers as you get lighter.

Macro calculators for every goal

This page is tuned for fat loss. The same validated formula powers calculators for the other goals:

Want your maintenance calories first? Start with our TDEE calculator, then come back here to split them into macros.