The short version
Estimate your maintenance calories, subtract 15 to 25 percent, eat that amount consistently for two to three weeks, then adjust based on what your weekly average weight actually does. That is the whole method. Everything below explains how to do each step well.
The reason it works is energy balance. When you eat less energy than you burn, your body makes up the difference from stored energy, mostly fat if you keep protein high and keep lifting. The formula gives you a starting point. Your own scale data tells you the real answer.
Step 1: estimate your maintenance calories
Maintenance, or total daily energy expenditure (TDEE), is the number of calories you burn in a typical day. It has four parts: your basal metabolic rate (BMR), the energy you spend digesting food, deliberate exercise, and all the incidental movement you do without thinking, such as walking, standing and fidgeting.
The quickest way to estimate it is our TDEE calculator. It uses the Mifflin-St Jeor equation for BMR, which a 2005 review in the Journal of the American Dietetic Association (Frankenfield et al.) found to be the most accurate of the common equations for most adults, and multiplies it by an activity factor.
Men: BMR = 10 x weight (kg) + 6.25 x height (cm) - 5 x age + 5
Women: BMR = 10 x weight (kg) + 6.25 x height (cm) - 5 x age - 161
Be honest with the activity level. Most people who train three or four times a week but sit at a desk all day are "lightly active", not "very active". Overestimating activity is the single most common reason a calculated deficit fails to produce weight loss.
| Activity level | Multiplier | Typical person |
|---|---|---|
| Sedentary | 1.2 | Desk job, little walking, no training |
| Lightly active | 1.375 | Desk job, 3 workouts a week, 5-7k steps |
| Moderately active | 1.55 | On feet part of the day or 4-5 hard sessions |
| Very active | 1.725 | Physical job or daily hard training |
| Extremely active | 1.9 | Manual labour plus training, or endurance athletes |
Step 2: choose the size of your deficit
A deficit expressed as a percentage of maintenance scales sensibly with body size. A 500 calorie cut is mild for a large, active man and aggressive for a small, sedentary woman.
| Deficit | Expected loss per week | Best for |
|---|---|---|
| 10-15% | 0.25-0.5% of bodyweight | Lean lifters, long diets, recomposition |
| 15-25% | 0.5-0.8% of bodyweight | Most people, most of the time |
| 25-30% | 0.8-1% of bodyweight | Higher body fat, short focused phases |
A useful guardrail from sports nutrition research is a loss rate of roughly 0.5 to 1 percent of bodyweight per week. Helms and colleagues, writing in the Journal of the International Society of Sports Nutrition in 2014, recommended this range for lifters who want to keep muscle while dieting. Slower is safer for muscle; faster is fine if you carry more fat.
If you prefer a target date, our weight loss calculator works backwards from your goal weight and tells you whether the timeline you have in mind is realistic.
A worked example
Take a 32-year-old woman who is 165 cm (5 ft 5 in) tall, weighs 75 kg (165 lb), works at a desk and lifts three times a week.
- BMR: 10 x 75 + 6.25 x 165 - 5 x 32 - 161 = 1,460 kcal.
- TDEE: 1,460 x 1.375 (lightly active) = about 2,010 kcal.
- Deficit of 20%: 2,010 x 0.8 = about 1,600 kcal per day.
- Expected loss: roughly 0.4-0.6 kg (1-1.3 lb) per week, which is 0.5-0.8% of her bodyweight. Right in the target range.
Now a 28-year-old man, 180 cm (5 ft 11 in), 95 kg (209 lb), moderately active. His BMR is about 1,940 kcal, his TDEE about 3,000 kcal, and a 20% deficit puts him near 2,400 kcal. Same method, very different number, which is why copying someone else's diet rarely works.
Step 3: set protein first, then fill in the rest
Calories decide how much weight you lose. Protein has a big say in whether that weight comes from fat or muscle. Aim for about 1.6 to 2.2 g of protein per kg of bodyweight (0.7 to 1 g per lb) while dieting. If you carry a lot of body fat, base it on your goal weight instead.
Once protein is set, keep fat at roughly 20 to 35 percent of calories, which supports hormones and makes meals satisfying, and give the remainder to carbohydrates to fuel training. The macro calculator does this split for you, and the protein guide covers the reasoning in detail.
Step 4: track for two weeks before changing anything
The formula is an estimate. Individual metabolic rates vary by a few hundred calories either way, and food labels are allowed to be off too. So treat your first number as a hypothesis and test it.
- Weigh yourself every morning, after the toilet, before food or drink.
- Log your intake as accurately as you can. A cheap kitchen scale beats guessing.
- Compare weekly averages, not single days. Water, salt, carbs and digestion can swing daily weight by 1-2 kg.
- Ignore the first week. Initial drops are mostly water and glycogen.
If your weekly average has not moved in two to three weeks and you have tracked honestly, cut 150-250 kcal per day or add 2,000-3,000 daily steps. Make one change at a time.
Why the numbers stop working, and what to do
As you lose weight, your maintenance drops. A lighter body costs less to run and to move, and most people unconsciously move less when dieting. This is why a deficit that worked brilliantly in month one can stall in month three.
The fix is simple: recalculate your maintenance every 4 to 5 kg (10 lb) lost, and keep an eye on your step count, since a drop in everyday movement can quietly erase a few hundred calories of deficit. If you have been dieting for more than 12 weeks and you feel flat, a one or two week break at maintenance often helps adherence more than it slows progress.
Common mistakes that hide a deficit
- Weekend drift. A 500 kcal daily deficit Monday to Friday is 2,500 kcal. Two relaxed weekend days at +1,200 each wipe out most of it.
- Untracked liquids and oils. A tablespoon of oil is about 120 kcal. Lattes, juices and alcohol add up fast.
- Eating back exercise calories. Fitness trackers often overestimate burn. Use the calories burned calculator as a rough guide and eat back half at most.
- Cutting too hard. Very large deficits raise hunger, wreck training and usually end in a rebound.
When to be careful
Calorie counting is a tool, not a requirement. If tracking makes you anxious or you have a history of disordered eating, work with a doctor or registered dietitian instead. The same applies if you are pregnant or breastfeeding, under 18, or managing a condition such as diabetes, where changes in intake can affect medication.
As a floor, most adults should not routinely eat below their BMR without medical supervision. If your calculated target falls under it, slow down the rate of loss and move more rather than eating less.
Frequently asked questions
How many calories should I eat to lose 0.5 kg a week?
A common rule of thumb is a daily deficit of about 500 kcal, since a kilogram of body fat stores roughly 7,700 kcal. Real-world loss is less predictable than the arithmetic, so set the deficit, then check your weekly average after two to three weeks and adjust.
Is 1,200 calories a day enough?
For some small, sedentary women it can be a reasonable short-term target, but for most adults it is too low and makes protein and micronutrient needs hard to meet. Calculate your own BMR and TDEE rather than using a generic number.
Should I count calories on rest days differently?
You can keep calories the same every day for simplicity, or move some carbohydrates from rest days to training days. What matters most is your weekly average intake.
Why am I not losing weight in a calorie deficit?
Usually because the deficit is smaller than you think, through overestimated activity, untracked food or weekend overeating, or because water retention is masking fat loss. Track carefully for two more weeks and compare weekly averages before changing anything.
General information for healthy adults, not medical advice. See our medical disclaimer.
