How to Calculate Your Macros for Weight Loss

Updated: June 7, 2026 · By Anthony Collova, founder of IIFYM.com

Nutrient-dense plate of food with clean macros for weight loss

To calculate your macros for weight loss, find your total daily energy expenditure (TDEE), subtract a deficit of 15 to 20 percent, then divide the remaining calories into protein at 0.8 to 1 gram per pound of body weight, fat at about 25 percent of total calories, and carbohydrates filling whatever calories are left. Most people land somewhere between 1,400 and 2,200 calories a day depending on size, age, and activity, and the whole calculation takes about five minutes by hand or 60 seconds with the IIFYM Macro Calculator. Macros are the only place your calories come from. Hit your macro targets and you hit your calorie target automatically, which is why macro tracking has stayed the most reliable approach to fat loss for over a decade. This guide walks through the exact math, step by step, with a full worked example using real numbers.

What Macros Actually Are

Macros, short for macronutrients, are the three nutrients your body needs in large amounts: protein, carbohydrates, and fat. Each one carries a fixed number of calories per gram. Protein and carbohydrates each contain 4 calories per gram. Fat contains 9 calories per gram. Alcohol, for the record, contains 7 calories per gram, though your body doesn’t require it. When you track macros, you control the source of your calories alongside the total. That control is what protects muscle while you lose fat. Two people can eat 1,800 calories a day and get completely different results depending on how those calories split across protein, carbs, and fat.

Step 1: Find Your TDEE

Your TDEE is the total number of calories you burn in a day, including everything from breathing to walking to training. It’s built from your basal metabolic rate (BMR), the calories you burn at rest, multiplied by an activity factor. The Mifflin-St Jeor equation is the standard starting point and the same formula the IIFYM calculator runs underneath. For a hand calculation:

BMR for women: (10 × weight in kg) + (6.25 × height in cm) − (5 × age) − 161
BMR for men: (10 × weight in kg) + (6.25 × height in cm) − (5 × age) + 5

Then multiply your BMR by an activity factor: 1.2 for sedentary, 1.375 for lightly active, 1.55 for moderately active, and 1.725 for very active. The result is your TDEE.

Step 2: Set Your Calorie Deficit

Fat loss requires eating fewer calories than you burn. A deficit of 15 to 20 percent below your TDEE strips fat while keeping the deficit livable. Drop too low and you lose muscle, your energy tanks, and adherence falls apart within a few weeks. For a TDEE of 2,000 calories, a 20 percent deficit puts you at 1,600 calories a day. That pace generally produces about 1 to 1.5 pounds of fat loss per week for most people, which is sustainable and repeatable.

Step 3: Set Your Protein

Protein comes first because it does the most work. It preserves lean muscle during a deficit, keeps you full, and carries the highest thermic effect of the three macros, meaning your body burns more calories digesting it. Set protein at 0.8 to 1 gram per pound of body weight. A 165-pound person lands at roughly 132 to 165 grams of protein per day. At 4 calories per gram, 150 grams of protein accounts for 600 calories.

Step 4: Set Your Fat

Fat supports hormone production, vitamin absorption, and satiety, so it should stay above about 0.3 grams per pound of body weight. A common starting point is 25 percent of total calories from fat. On a 1,600-calorie target, 25 percent comes to 400 calories from fat. At 9 calories per gram, that’s about 44 grams of fat per day.

Step 5: Fill the Rest With Carbs

Carbohydrates take whatever calories remain after protein and fat are set. Carbs fuel training, recovery, and daily energy. Using the running example: 1,600 total calories, minus 600 from protein, minus 400 from fat, leaves 600 calories for carbs. At 4 calories per gram, that’s 150 grams of carbohydrates per day.

A Worked Example

The full calculation for a 35-year-old woman, 165 pounds (75 kg), 5 feet 6 inches (168 cm), moderately active, who wants to lose fat:

BMR: (10 × 75) + (6.25 × 168) − (5 × 35) − 161 = 1,464 calories
TDEE: 1,464 × 1.55 = 2,269 calories
20 percent deficit: about 1,815 calories
Protein: 165 grams (660 calories)
Fat: 25 percent of 1,815 = 454 calories, about 50 grams
Carbs: 1,815 − 660 − 454 = 701 calories, about 175 grams

Macro breakdown pie chart: 165g protein, 50g fat, 175g carbs for a 1,815-calorie weight loss day

Her daily targets come out to roughly 1,815 calories, 165 grams of protein, 50 grams of fat, and 175 grams of carbs. Those are starting numbers. After two to three weeks of consistent tracking and weekly weigh-ins, she adjusts based on what the scale and the mirror actually show.

Why a Calculator Beats Hand Math

The math above works, and it’s worth understanding once. Doing it by hand every time your weight or activity changes is where most people give up. The IIFYM Macro Calculator runs the same Mifflin-St Jeor equation, applies your goal and activity level, and returns your protein, fat, and carb targets in about 60 seconds. It was the first macro calculator ever built, launched in 2012, and more than 10 million people have used it since.

IIFYM Macro Calculator showing protein, carb, and fat results for weight loss

Calculate your macros free with the IIFYM Macro Calculator → Related tools and guides: the TDEE Calculator to find your maintenance calories, the Keto Macro Calculator if you’re running low-carb, and the IIFYM weight loss calculators hub for the full set.

A Note on Accuracy

Every calculation here gives you a starting point grounded in your real body data. No formula predicts your metabolism perfectly. Track consistently for two to three weeks, watch your weekly average weight, and adjust calories up or down by 100 to 150 at a time. This information is educational and isn’t a substitute for guidance from a doctor or registered dietitian, especially if you have a medical condition.

Frequently Asked Questions

How do I calculate my macros for weight loss?

Find your TDEE, subtract 15 to 20 percent for a deficit, then set protein at 0.8 to 1 gram per pound of body weight, fat at about 25 percent of calories, and carbs with the remaining calories. A 165-pound person in a moderate deficit typically lands near 150 grams protein, 50 grams fat, and 175 grams carbs.

What is the best macro ratio for fat loss?

No single ratio fits everyone, because protein scales with body weight rather than a flat percentage. A reliable starting framework is roughly 30 percent protein, 25 to 30 percent fat, and 40 to 45 percent carbohydrates, then adjusted to your size, activity, and how your body responds over the first few weeks.

How many calories should I eat to lose weight?

Eat 15 to 20 percent below your TDEE. For someone burning 2,200 calories a day, that’s about 1,760 to 1,870 calories. This range produces roughly 1 to 1.5 pounds of fat loss per week for most people, while keeping enough food to protect muscle and stay consistent.

Do I have to count macros to lose weight?

Counting macros isn’t strictly required, though it’s the most accurate way to control results. Tracking macros guarantees you hit both your calorie target and enough protein to hold onto muscle. Many people start by tracking only protein and total calories, then add full macro tracking once the habit sticks.

How accurate is a macro calculator?

A macro calculator gives an evidence-based estimate within about 5 to 10 percent of your true needs, because it uses validated equations like Mifflin-St Jeor. Your real numbers depend on individual metabolism, so the calculator sets your starting point and your own progress data fine-tunes it over the following weeks.

About the Author

This guide was written by Anthony Collova, founder of IIFYM.com and creator of the original “If It Fits Your Macros” macro calculator, built in 2012. Anthony has spent more than 15 years coaching people through fat loss, flexible dieting, and body recomposition, with over 10 million macro profiles created through the IIFYM system.