How Many Calories to Lose 1 kg? The Real Math (2026)

How many calories to lose 1 kg? You need roughly a 7,700 kcal deficit to lose about 1 kg of body fat, which works out to a 500 kcal/day deficit for around 0.45 kg per week. Trainera's free calorie calculator and TDEE calculator turn that math into a personal daily target in seconds.

Where the 7,700 kcal figure comes from

Body fat stores a lot of energy. A pure kilogram of fat holds close to 9,000 kcal, but body-fat tissue also contains water and connective structures, so the widely used estimate for the energy in 1 kg of body fat is about 7,700 kcal (roughly 3,500 kcal per pound). This is the single most useful "calories per kg fat" number for planning weight loss.

So the answer to "how many calories to lose 1 kg" is: create a cumulative deficit of around 7,700 kcal. You never have to do that in one day, though. You spread it across a week or more with a modest daily calorie deficit to lose a kilo safely.

Turning 7,700 kcal into a daily deficit

The practical question is "how much of a deficit to lose weight each week?" Divide the weekly deficit you want by seven. A 500 kcal/day deficit adds up to 3,500 kcal per week, which is roughly 0.45 kg (about one pound) of fat. Double that and you approach 1 kg per week, but the bigger the deficit, the harder it is to sustain and the more muscle and energy you risk losing.

Deficit to weekly loss table

These are estimates for the energy math, not promises the scale will match exactly. For most people a 300-600 kcal daily deficit is the sweet spot: fast enough to see progress, gentle enough to keep energy, training performance, and muscle.

A quick worked example makes the calories per kg fat idea concrete. Say you want to lose 5 kg. Five kilos of fat is roughly 5 x 7,700 = 38,500 kcal. At a 500 kcal/day deficit that's 38,500 / 500 = 77 days, or about 11 weeks. Bump the deficit to 750 kcal/day and the same 5 kg takes roughly 51 days, about 7-8 weeks. Neither timeline is "right" — the slower one is easier to sustain and protects muscle, while the faster one demands tighter tracking and more discipline. Pick the pace you can actually hold for the whole stretch, because a deficit you abandon in week three loses to a smaller deficit you keep for three months.

Step 1: find your TDEE and maintenance calories

You can't set a deficit until you know your Total Daily Energy Expenditure (TDEE) — the calories you burn per day at your current weight and activity level. Subtract your chosen deficit from TDEE and you have your daily eating target. Run the numbers with the free Trainera TDEE calculator, then confirm your intake goal with the calorie calculator. Want your protein, carbs, and fat split too? The macro calculator builds it around that same target.

Example: if your TDEE is 2,400 kcal and you eat 1,900 kcal per day, that's a 500 kcal deficit — on paper, about 0.45 kg of fat per week and roughly 1 kg every ~2.2 weeks.

Two practical cautions. First, calculators give an estimate, not a lab measurement — your true maintenance could sit 100-200 kcal above or below the number, so treat the first two weeks as a calibration period and adjust based on what the scale trend actually does. Second, don't set your intake dangerously low just to speed things up. Most adults should not drop below roughly 1,200-1,500 kcal per day without guidance; going too low tanks energy, training, sleep, and hormones, and it rarely produces faster fat loss than a moderate deficit anyway.

Why real-world loss rarely matches the math

The 7,700 kcal model is a planning tool, not a perfect prediction. Several real factors make weekly scale readings jump around:

• Water weight. Sodium, carbs, stress, sleep, and (for women) the menstrual cycle can swing scale weight by 1-2 kg overnight — completely independent of fat loss.
• Adherence gaps. Untracked bites, sauces, oils, and weekend meals quietly shrink your real deficit. Consistent logging is what closes the gap between plan and reality.
• TDEE drifts down. As you get lighter you burn fewer calories, and you may unconsciously move less. A deficit that worked at the start slowly becomes maintenance, so targets need periodic recalculation.
• Muscle and glycogen. New training, more protein, and refilling glycogen stores can add lean mass and water even while you lose fat, masking progress on the scale.

The fix is to judge trends over 2-4 weeks, not day to day. Weigh consistently, average the readings, and track waist measurements and photos alongside weight. Trainera logs weight, macros, and progress trends together so you see the moving average instead of reacting to daily noise.

This is also why the classic "3,500 kcal per pound" rule overpredicts long-term loss. It was derived from the energy content of fat, but it assumes your metabolism stays fixed, which it doesn't. As you diet, your body burns fewer calories per day and adaptive changes accumulate, so a deficit that dropped 0.45 kg in week one may drop noticeably less by month three at the same intake. That's normal and expected — it's not a broken metabolism, and it's not a reason to slash calories to nothing. The right response is a periodic recalculation of your TDEE and, if progress has truly plateaued for 3-4 weeks at consistent intake, a small further cut, a short diet break at maintenance, or a bump in daily activity.

What a safe rate of loss looks like

For sustainable fat loss, aim for about 0.5-1% of your body weight per week. An 80 kg person, that's roughly 0.4-0.8 kg weekly. Slower is often better if you're already lean or want to keep hard-earned muscle. Going faster with a very large deficit tends to backfire: more muscle loss, worse gym sessions, stronger hunger, and higher odds of rebound eating. Pair your deficit with resistance training and 1.6-2.2 g of protein per kg of body weight to hold onto muscle — see the bulking and cutting complete guide for how to structure it.

Tracking it without the guesswork

Knowing you need a 500 kcal deficit is easy; hitting it every day is the hard part. That's where an accurate tracker earns its keep. Trainera gives you per-meal macro tracking on USDA food data and recipes, barcode scanning, AI food-photo analysis, AI shopping lists, and weekly AI insights that flag when your intake or trend is drifting. Because Trainera is an all-in-one platform, your calorie target, macros, workouts, and body-weight trend all live in one place — no juggling three apps. If you're comparing loggers, the best macro tracking app roundup and best MyFitnessPal alternatives break down the options.

A few habits make the deficit far easier to hold. Weigh and log your food rather than eyeballing portions — cooking oils, nut butters, and sauces are calorie-dense and easy to underestimate by hundreds of calories. Front-load protein and fibre so you feel full on fewer calories; both blunt hunger and protein defends muscle in a deficit. Keep training with weights so the weight you lose is fat, not hard-won muscle. And log consistently, weekends included, because the difference between people who reach their goal and people who stall is almost always adherence, not metabolism or the choice of app. Trainera's streaks and achievements — for calories, protein, workouts, and progressive overload — exist precisely to keep that daily consistency going when motivation dips.

FAQ-style quick answers

A 500 kcal daily deficit is the classic starting point for steady, sustainable loss of around 0.45 kg per week. If you're in a hurry, a larger deficit loses weight faster but is harder to sustain and costs more muscle — which is why most coaches favor a moderate, trackable deficit you can actually keep.

Conclusion

To lose 1 kg of fat you need to burn roughly 7,700 kcal more than you eat — most safely delivered as a 300-600 kcal daily deficit that adds up over one to three weeks. Find your TDEE, set your target, track honestly, and judge progress by the multi-week trend, not the daily scale. Trainera is the all-in-one way to do all of it: free TDEE, calorie, and macro calculators, AI food logging, workout building, and progress tracking in a single app at one price. Create your free Trainera account and turn the math into results.

Related reading

• Bulking and Cutting: The Complete Guide
• The Best Macro Tracking App
• Best MyFitnessPal Alternatives
• MacroFactor vs MyFitnessPal
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