About this calculator
The Weight Loss Calculator estimates daily calories and time to goal from current weight, target weight, activity, and weekly loss goal. It is designed for safe planning rather than aggressive dieting.
Weight Loss Calculator method
This calculator uses standard health, nutrition, exercise, or measurement formulas to create an educational estimate. Results are designed for planning and comparison, not diagnosis.
- 1kg body fat is roughly 7,700 kcal
- daily deficit = weekly loss x 7,700 / 7
- daily calories = TDEE - daily deficit
How to use the weight loss calculator
- Enter the requested body measurement, activity, food, time, or goal details.
- Check the units carefully before using the result.
- Review the main result and the supporting breakdown.
- Use the worked examples and reference table to sense-check the result.
- Adjust assumptions if your real situation differs from the default values.
Worked examples
Moderate plan
Input: 85kg to 75kg, 0.5kg/week
Calculation: 10kg to lose / 0.5kg per week
Result: About 20 weeks
Slow plan
Input: 80kg to 76kg, 0.25kg/week
Calculation: 4kg / 0.25kg per week
Result: About 16 weeks
When this calculator is useful
Use this tool for quick planning, comparison, or learning the method behind the calculation. It is especially useful when you want a transparent estimate rather than a black-box app result.
Common mistakes
- Mixing units
- Entering inches where centimetres are expected, or miles where kilometres are expected, can make the answer look plausible but wrong.
- Treating estimates as exact
- Health and fitness formulas are averages. Real bodies vary with age, sex, medication, fitness, sleep, illness, and measurement accuracy.
Health and safety note
This calculator is for general information only and is not medical advice. Speak to a GP, health visitor, dietitian, qualified coach, or other relevant professional before making health decisions, especially for children, pregnancy, alcohol, medical conditions, or restrictive diets.
Frequently asked questions
Is this result exact?
No. It is an estimate based on common formulas and typical assumptions. Use it as a guide, not a clinical measurement.
Can I use this for medical decisions?
No. It can help you understand the numbers, but medical decisions should be discussed with a qualified professional.
Why does my wearable or app show a different number?
Different tools use different assumptions, sensors, and formulas. Terrain, fitness, body composition, and measurement technique can all change the result.
Should children use adult health categories?
No. Children need age- and sex-adjusted interpretation. Adult BMI and weight categories do not apply directly to children.
How should I use the result?
Use it to compare scenarios, plan goals, or understand the formula. Recheck with real-world progress and professional guidance where needed.
Related calculators
- Calorie Calculator
- TDEE Calculator
- Macro Calculator