How to Calculate Your Calories and Macros for Fat Loss

Most people know they need a calorie deficit to lose fat. What they don’t know is what that actually means in practice — what number to eat to, how much protein to aim for, and where fat and carbs fit in. The result is usually either no plan at all, or a vague attempt to “eat less” that falls apart within two weeks.

These are the steps. Work through them once and you’ll have a set of real numbers to work from.

Step 1: Find Your TDEE and Set a Calorie Target

TDEE stands for Total Daily Energy Expenditure. It’s the total number of calories your body burns in a day — movement, exercise, digestion, and everything your body does just to keep you alive. It’s your maintenance number: eat at your TDEE and your weight stays roughly the same; eat below it and you lose; eat above it and you gain.

The most practical way to find yours is to use an online calculator. The Chazzen Fitness calculator does this — it takes your age, sex, weight, height, and activity level and returns your TDEE alongside a full macro breakdown. If you enter your body fat percentage it also uses a more accurate formula based on your lean body mass.

One thing worth paying attention to when setting your activity level: input the level that reflects what you’re actually going to be doing, not what you’re doing right now. If you’re starting a new training programme, factor that in. Most calculators have options ranging from sedentary to very active — be honest about where you’ll land once you’re underway.

Once you have your TDEE, set your calorie target:

• To lose fat: subtract 300–500 calories. This is a moderate deficit that produces consistent fat loss without being aggressive enough to cause rapid muscle loss or tank your energy.
• To maintain weight: eat at your TDEE.
• To build muscle slowly: add 100–200 calories. This is a lean surplus — enough to support muscle growth without gaining fat quickly.

For most people starting out, a 500-calorie deficit is a good starting point. That equates to roughly 0.5kg (1lb) of fat per week, assuming the tracking is accurate.

Step 2: Calculate Your Protein

Protein is the most important macro to set in a fat loss phase. It preserves muscle while you’re in a deficit, it keeps you fuller than carbs or fat gram-for-gram, and it has a higher thermic effect — your body actually burns more calories digesting it than it does digesting the other macros.

The target: 1.6g of protein per kilogram of lean body mass. Lean body mass is your total weight minus your body fat. If you don’t know your body fat percentage, a rough estimate will do — or just use your total bodyweight. In pounds, the equivalent is 0.73g per lb of lean body mass.

• Lean body mass (kg) × 1.6 = daily protein target in grams
• Lean body mass (lbs) × 0.73 = daily protein target in grams

Once you have your protein in grams, multiply by 4 to get the calorie contribution from protein. Each gram of protein provides 4 calories.

Example: 70kg lean body mass × 1.6 = 112g protein. 112 × 4 = 448 calories from protein.

If you’d rather skip the manual maths, the Chazzen Fitness calculator calculates your protein range automatically and gives you a slider to adjust it and see how it affects your other macros in real time.

Step 3: Calculate Your Fat

Fat is the most calorie-dense macro at 9 calories per gram versus 4 for protein and carbs, so it needs a defined allocation rather than an open one. Going too low on fat impairs hormone function and makes the diet harder to sustain — dietary fat contributes to satiety and slows digestion.

A solid starting point is 30% of your total daily calories from fat.

• Total goal calories × 0.30 = calories from fat
• Calories from fat ÷ 9 = grams of fat

Example: 1,900-calorie target × 0.30 = 570 calories from fat. 570 ÷ 9 = 63g of fat per day.

Step 4: Calculate Your Carbs

Carbs are the flexible macro. They’re not the enemy, but they’re also the first thing to adjust if your numbers aren’t working. Once protein and fat are set, whatever calorie budget is left over goes to carbs.

• Total calories − calories from protein − calories from fat = calories remaining for carbs
• Calories from carbs ÷ 4 = grams of carbs

Continuing the example: 1,900 − 448 (protein) − 570 (fat) = 882 calories from carbs. 882 ÷ 4 = 220g of carbs per day.

Your full starting split would be: 1,900 kcal / 112g protein / 63g fat / 220g carbs. These are your starting numbers — not permanent, not perfect, just a calibrated starting point.

Step 5: Build a Plan That Makes These Numbers Achievable

Having numbers is not the same as having a plan. The next step is building eating habits that make hitting your calorie and protein targets realistic day-to-day.

Total calories and protein are the two numbers that matter most. Track those two closely. Fat and carbs can flex within reason — as long as you’re not going extremely low on either, they’re secondary. Chasing perfect macros on top of perfect calories adds a layer of complexity most people don’t need, especially early on.

Practically, this means building meals around protein sources first — chicken, fish, eggs, Greek yoghurt, cottage cheese, lean mince, tuna — and filling in carbs and fats around them. If protein is covered in every meal, hitting your daily target becomes far less of an effort.

Use a food tracking app if you’re new to this. A kitchen scale removes the guesswork that tends to quietly wreck a deficit. You don’t need to aim for perfection — tracking with 80–90% accuracy consistently over months produces real results. Tracking perfectly for two weeks and burning out doesn’t.

Step 6: Weigh Yourself Consistently and Adjust

The numbers you calculated are estimates. They’re good estimates based on established formulas, but they’re not exact. Your actual TDEE depends on factors no calculator can fully account for — how much you move throughout the day without thinking about it, metabolic adaptation over time, and individual variation.

This is why the scale is your feedback loop, not your judge.

Weigh yourself under the same conditions every day: right after waking up, before eating or drinking anything including water, after going to the bathroom, with minimal clothing. Log the number. Don’t react to a single reading — body weight fluctuates daily based on water, sodium, hormones, and digestion. Look at the weekly average instead.

If your weight is trending in the right direction over 2–3 weeks, your numbers are working. If it’s not moving, or moving in the wrong direction:

• Check your tracking first. Underestimating portions is the most common reason a deficit stalls — especially with calorie-dense foods like oils, nuts, and cheese.
• If your tracking is solid and the scale still isn’t moving after 2–3 weeks, reduce your calorie target by 100–150 and adjust.

The numbers you start with are not the numbers you’ll always use. The goal is to start somewhere accurate, observe what the scale does, and adjust based on what’s actually happening — not based on what a formula told you once.

The Short Version

Use a calculator to find your TDEE. Subtract 300–500 for fat loss. Set protein at 1.6g per kg of lean mass, fat at 30% of total calories, carbs with whatever’s left. Prioritise total calories and protein above everything else. Weigh yourself consistently and adjust if the scale doesn’t move after a few weeks.

That’s it. The rest is execution.