Weight Loss Calculator
Calculate the daily and weekly calorie deficit needed to lose weight by your target date — with feasibility check based on safe weight loss guidelines.
Reviewed October 7, 2026 Runs in your browser — inputs are never stored
This tool provides general sports and fitness estimates for educational purposes only. It is not medical advice — consult a physician before starting or intensifying training, especially if you have a cardiovascular condition.
About the Weight Loss Calculator
The weight loss calculator works out the daily calorie deficit needed to reach a target weight by a deadline, using the common estimate that about 7,700 kcal of deficit is needed per kilogram of body fat. It also shows the weekly rate so you can check the plan is realistic; most guidelines recommend 0.5–1 kg per week. Real weight loss slows over time as the body adapts.
How to use it
- 1Enter your current weight.
- 2Enter your target weight.
- 3Enter the number of weeks and press Calculate.
Worked example
going from 85 kg to 78 kg in 14 weeks needs a total deficit of about 7 × 7,700 = 53,900 kcal, or 550 kcal per day — a rate of 0.5 kg a week.
How it works
Formula
Total Deficit = (Current − Target) × 7,700 kcal. Daily Deficit = Total ÷ (Weeks × 7).
Common use cases
- Setting a realistic deadline
- Checking whether a goal is safe
- Planning daily calorie targets
Common mistakes to avoid
- Choosing a deadline that requires more than about 1 kg of loss a week.
- Ignoring that weight loss slows as you get lighter.
Frequently asked questions
A:Approximately 7,700 calories (kcal) per kilogram of body fat — the standard used in weight loss planning.
A:Most health guidelines recommend 0.5–1 kg per week as sustainable. More than 1 kg/week may cause muscle loss.
A:Yes — diet alone creates a calorie deficit. However, combining exercise with diet is more effective and sustainable.
A:1 kg/week is the maximum recommended rate; 10 kg in 10 weeks is at the upper limit of safe loss.
A:Extend your timeframe or combine diet and exercise. Deficits above 1,000 kcal/day are generally not recommended.
Reviewed for accuracy · Last updated October 7, 2026
Formulas follow published sports-science literature and official league definitions (Karvonen heart rate reserve, Cooper and Bruce protocols, MET compendium values, and standard baseball, cricket, and basketball statistics).
CalcWisee Editorial Team
Calculator development and formula review
CalcWisee is an independent site founded by Ayman. Every calculator is built from a published formula or official definition, tested against hand-worked examples before it goes live, and corrected promptly when a reader reports an issue to ayman@calcwisee.com.
Expertise: Financial mathematics, Health and fitness formulas, Applied mathematics, Unit conversion standards
References & sources