Weight Loss Calculator
See how long to reach your goal weight at your chosen weekly loss rate.
Written by Golam Rabbani, Founder & Lead Engineer — Last updated 2026-05-01
How to use this weight loss calculator
- Enter your current weight and select kg or lbs using the unit toggle.
- Enter your goal weight in the same unit.
- Select a weekly loss goal from the four radio options (0.25 to 1 kg/week).
- Press Calculate to see your total to lose, daily calorie deficit, weeks to goal, and estimated goal date.
- Use Copy to save the result, or Reset to clear all inputs.
About this weight loss calculator
The weight loss calculator takes your current weight, goal weight, and desired weekly loss rate to estimate how long it will take to reach your target and what daily calorie deficit that requires.
The weight loss calculator uses the widely cited 7,700 kcal-per-kilogram rule: to lose one kilogram of body fat requires a cumulative deficit of roughly 7,700 kcal. From your chosen weekly rate (0.25 kg, 0.5 kg, 0.75 kg, or 1 kg per week), the tool calculates the required daily deficit as weekly rate × 7,700 ÷ 7. The total weeks to goal is the weight difference in kilograms divided by the weekly rate, rounded up to a whole week, and the estimated goal date counts that many weeks forward from today. Entering weights in lbs converts them to kg internally before the calculation. This is an estimate for general information and is not a substitute for advice from a qualified clinician.
For example, if your current weight is 85 kg and your goal is 70 kg at 0.5 kg per week, the tool shows 15 kg to lose, a daily deficit of 550 kcal, 30 weeks to goal, and an estimated goal date roughly seven months from now. This makes the calculator useful for anyone planning a structured weight management programme and wanting a concrete timeline. This calculator is for general educational purposes only and is not medical advice — consult a licensed healthcare professional for personal guidance.
FAQ
- How does the weight loss calculator estimate time to goal?
- It divides the total kilograms to lose by your chosen weekly rate and rounds up to the nearest whole week. It then counts that many weeks forward from today to produce the estimated goal date.
- What formula does the tool use for the daily calorie deficit?
- It applies the 7,700 kcal-per-kilogram rule: daily deficit = weekly rate (kg) × 7,700 ÷ 7. For the default 0.5 kg/week pace that works out to a 550 kcal daily deficit.
- How accurate is this weight loss calculator?
- The timeline and deficit are estimates based on a simplified energy-balance model. Individual results vary with metabolism, activity level, and body composition. The result is for general planning only and is not a substitute for advice from a qualified clinician.
- What happens if I enter a goal weight equal to or higher than my current weight?
- The calculator shows an error and does not produce a result. Goal weight must be strictly less than current weight for the calculation to make sense.
- Does the weight loss calculator store my data?
- No. The weight loss calculator runs entirely in your browser. Your weights and settings are never sent to a server, logged, or saved between visits — closing the page clears everything.
- Is the weight loss calculator free?
- Yes. It is free to use with no signup, no account, and no usage limit.