Cutting means eating in a calorie deficit to lose fat while keeping as much muscle as possible. The deficit drives the fat loss, but your macro split decides whether the weight you lose is fat or hard-earned muscle. This fat loss macro calculator does the math for you: enter your stats and get daily protein, carb, and fat targets built for a cut.
Enter your details below. For the classic cutting setup, choose the “Lose weight (cut)” goal and the “High protein” preset tab, which configures this page as a macro calculator for fat loss. It estimates your calories with the Mifflin-St Jeor equation and splits them into protein, carbs, and fat.
How the math works
Step 1 – BMR (Mifflin-St Jeor, 1990): Men: 10 x weight(kg) + 6.25 x height(cm) – 5 x age + 5. Women: same, but – 161 instead of + 5. BMR is what you burn at complete rest.
Step 2 – TDEE: BMR multiplied by your activity factor (1.2 sedentary up to 1.9 extremely active) gives total daily energy expenditure.
Step 3 – Goal adjustment: a 500 kcal daily deficit for fat loss, maintenance for staying the same, or a 300-500 kcal surplus for muscle gain.
Step 4 – Macro split: the preset percentages are applied to your calorie target. Protein and carbs count 4 kcal per gram, fat counts 9 kcal per gram.
The Best Macro Split for Cutting
There is no single magic ratio, but research favors a high-protein split: roughly 35-40% protein, 30-35% carbs, and 25-30% fat. Protein is the priority because it preserves muscle in a deficit and keeps you full. Carbs fuel your training; fat stays moderate to support hormones. The “High protein” preset in this weight loss macro calculator uses exactly this split.
How Much Protein When Cutting?
Aim for 1.8 to 2.2 grams of protein per kilogram of bodyweight (0.8-1.0 g per lb). An 80 kg person cutting should target roughly 145-175 g of protein daily. This is higher than maintenance because a calorie deficit increases muscle breakdown, and protein is your main defense. Run your stats through this free macro calculator for weight loss and it will set that protein number for you automatically.
How Big Should Your Deficit Be?
A 300-500 calorie daily deficit loses about 0.5 kg (1 lb) per week: fast enough to see progress, slow enough to keep muscle and stay sane. Bigger deficits cost disproportionately more muscle. To plan your exact daily target from your goal weight and deadline, use our calorie deficit calculator.
Frequently Asked Questions
Will I lose muscle while cutting?
Some muscle loss is normal in a deficit, but high protein (1.8-2.2 g/kg), regular strength training, and a moderate 300-500 calorie deficit keep it minimal. Crash diets are what cost you muscle.
How long should a cutting phase last?
Most cuts run 8-16 weeks. Longer cuts benefit from 1-2 week diet breaks at maintenance to manage hunger and fatigue. When you reach your goal leanness or progress stalls for 3+ weeks, end the cut.
Should I cut carbs to lose fat faster?
No. Fat loss comes from the calorie deficit, not from fearing carbs. Keep carbs as high as your calorie budget allows while hitting your protein target — your training performance will thank you.
Do I need cardio to cut?
Cardio helps but the deficit matters most. Two to four sessions of 20-30 minutes per week is plenty for most people. Daily steps (8,000-10,000) are the underrated fat-loss tool.