Trying to answer “how many calories should I eat to lose weight?” starts with an estimate, not a perfect number. This calorie deficit planner shows how to estimate resting needs and total daily energy expenditure (TDEE), choose a moderate deficit, set a practical protein target, and track results over 12 weeks so you can adjust based on real-world progress.
Overview
A calorie deficit occurs when you consistently use more energy than you consume. A calorie deficit calculator can provide a useful starting point, but its result is an estimate because energy needs vary with body size, activity, sleep, muscle mass, health status, and changes in routine.
The basic workflow is:
- Collect your current weight, height, age, sex used for the equation, and typical activity level.
- Estimate your basal metabolic rate (BMR), or the energy your body may use at rest.
- Multiply BMR by an activity factor to estimate TDEE.
- Choose a moderate deficit rather than the largest possible reduction.
- Monitor your average weight, waist measurement, hunger, energy, and training performance.
- Reassess after several weeks instead of reacting to one day’s scale reading.
This approach is more reliable than choosing a generic calorie target. Weight can fluctuate because of hydration, sodium, carbohydrate intake, digestion, menstrual-cycle changes, and exercise-related inflammation. A trend across multiple weeks is more informative than a single measurement.
How to estimate your calorie target
Step 1: Estimate BMR with Mifflin–St Jeor
The Mifflin–St Jeor equation is commonly used for an initial estimate. Enter weight in kilograms, height in centimetres, and age in years.
- For males: BMR = (10 × weight) + (6.25 × height) − (5 × age) + 5
- For females: BMR = (10 × weight) + (6.25 × height) − (5 × age) − 161
These sex-based equations are population estimates and may not represent every individual. If you are transgender, intersex, pregnant, breastfeeding, very muscular, or managing a medical condition, ask a qualified clinician or registered dietitian how to interpret an estimate for your circumstances.
Step 2: Multiply by activity level to estimate TDEE
TDEE is an estimate of the calories used across a full day, including resting metabolism, movement, and exercise. Select the activity description that best matches your usual week rather than your most active day.
| Activity description | Example multiplier |
|---|---|
| Mostly sedentary | 1.2 |
| Lightly active: some walking or light exercise | 1.35 |
| Moderately active: regular training or an active job | 1.5 |
| Very active: frequent hard training or substantial physical work | 1.7 |
| Extremely active: demanding training and physical work | 1.9 |
TDEE = BMR × activity multiplier. Activity factors are not universal standards. If you are unsure between two levels, start with the lower estimate and use your weight trend to refine it.
Step 3: Apply a moderate deficit
A practical starting point is often a reduction of about 10% to 20% below estimated TDEE. For example, a TDEE of 2,400 calories would produce an initial target of roughly 1,920 to 2,160 calories. A smaller deficit may be easier to sustain and may better support training, sleep, and adequate nutrition.
Do not treat a calculated target as permission to undereat. Very low-calorie diets can create nutritional risks and may require medical supervision. People who are pregnant or breastfeeding, adolescents, older adults at risk of muscle loss, athletes with high training demands, and anyone with diabetes, a history of an eating disorder, or another medical condition should seek individualized advice before deliberately restricting calories.
Step 4: Set protein and meal targets
Protein can help support muscle retention during weight loss, especially when paired with resistance training. A reasonable planning range for many adults is approximately 1.2 to 1.6 grams of protein per kilogram of body weight per day, but needs vary. A dietitian can personalize this range for kidney disease, pregnancy, athletic training, or other conditions.
Instead of searching for one “best macro ratio for fat loss,” set protein first, include a variety of minimally processed foods, and divide the remaining calories between carbohydrates and fats according to preference, health needs, and training demands. Include vegetables or fruit, a protein source, and a high-fibre carbohydrate or healthy fat at most meals.
Inputs and assumptions
Use consistent inputs so your estimate can be compared over time:
- Weight: Weigh under similar conditions, such as after waking and using the bathroom, while recognizing normal daily variation.
- Height: Measure without shoes. Height matters in both BMR equations and should not be guessed.
- Activity: Consider walking, work, structured exercise, and typical rest days. Do not automatically “eat back” every exercise-calorie estimate from a wearable.
- Body composition: If you know body-fat percentage from a reasonably consistent method, the Katch–McArdle equation can be another estimate.
For Katch–McArdle, estimate lean body mass in kilograms, then use: BMR = 370 + (21.6 × lean body mass). Lean body mass equals body weight multiplied by one minus body-fat percentage expressed as a decimal. For example, 30% body fat is entered as 0.30. Because home body-fat measurements can be imprecise, this method is not automatically more accurate than Mifflin–St Jeor.
Use the same method and conditions when tracking waist measurements. For a broader view of body composition, see the body fat percentage calculator guide and the waist-to-hip ratio measurement guide. A BMI result can provide context about weight relative to height, but it does not distinguish muscle, fat, or fat distribution; read the BMI calculator guide for limitations.
Worked examples
Example 1: Mifflin–St Jeor estimate
Suppose a 35-year-old female is 165 cm tall and weighs 80 kg. Her estimated BMR is:
(10 × 80) + (6.25 × 165) − (5 × 35) − 161 = approximately 1,505 calories per day.
If she describes her normal activity as moderate, using a 1.5 multiplier gives an estimated TDEE of about 2,258 calories. A 10% to 20% starting deficit would be approximately 1,805 to 2,032 calories. She could begin near the higher end if hunger or training demands are significant, then review the trend after three to four weeks.
Example 2: Katch–McArdle comparison
Suppose another adult weighs 90 kg and estimates 25% body fat. Lean body mass is 90 × 0.75, or 67.5 kg. Katch–McArdle estimates BMR at approximately 1,828 calories. If a 1.35 activity multiplier is appropriate, estimated TDEE is about 2,468 calories. A 10% to 20% deficit would be approximately 1,974 to 2,221 calories.
The two methods may produce different results. That does not mean one calculation has identified a guaranteed maintenance level. Choose a reasonable starting point, track the outcome, and adjust gradually.
Reusable weekly meal-plan template
Use this structure rather than repeating a rigid menu:
- Breakfast: protein-rich food plus fruit and a fibre-containing carbohydrate.
- Lunch: lean protein or beans, vegetables, a grain or starchy food, and a measured dressing or oil.
- Dinner: fish, poultry, tofu, beans, eggs, or another protein; two vegetables; and a satisfying carbohydrate portion.
- Snack options: Greek-style yogurt, fruit with nuts, cottage cheese, vegetables with hummus, or a protein-containing sandwich.
- Flexible foods: Reserve some calories for foods you enjoy so the plan does not depend on perfect restriction.
Adjust serving sizes to reach your calorie and protein targets. For more detailed planning, use the calorie deficit and macro calculator guide.
When to recalculate and how to track 12 weeks
Recalculate TDEE after an approximately 5% change in body weight, after a major change in activity, or about every 8 to 12 weeks. Recalculate sooner if your work schedule, training volume, medication, or health status changes substantially. Estimates usually become less useful when old body weight and activity inputs no longer reflect your current routine.
Use this simple 12-week tracker:
| Week | Average weight | Waist | Average calories | Protein average | Energy/training notes |
|---|---|---|---|---|---|
| 1 | _____ | _____ | _____ | _____ | _____ |
| 2–4 | _____ | _____ | _____ | _____ | _____ |
| 5–8 | _____ | _____ | _____ | _____ | _____ |
| 9–12 | _____ | _____ | _____ | _____ | _____ |
Review the weekly average, not isolated weigh-ins. If the trend is moving in the intended direction and you feel well, keep the target. If there is no meaningful trend after several consistent weeks, check portions, liquid calories, weekend eating, activity, and logging accuracy before making a small adjustment. If weight is dropping rapidly, hunger is persistent, energy is poor, or training performance is deteriorating, increase intake and seek professional guidance.
Finally, treat calorie calculations as planning tools rather than medical prescriptions. Revisit your inputs every 8 to 12 weeks, keep the tracker, and adjust one variable at a time. Sustainable weight management depends not only on calories, but also on adequate nutrition, movement, sleep, stress management, and a plan you can realistically repeat.
