Calorie Deficit Calculator
Work out the daily calorie target needed to reach a goal weight by a chosen date.
Last updated · View algorithm, constants and default inputs (JSON)
About this calculator
This is a static energy estimate: it uses 7,700 kcal per kilogram and assumes maintenance calories stay fixed. It does not model changes in energy needs or predict actual weight change. The result is not a personalized nutrition or medical recommendation. If the requested timeline produces a target of zero calories or less, the calculator asks you to choose a longer timeline.
Worked example
calculated with the default values below
Current weight 85 kg · Target weight 75 kg · Time available 20 weeks · Maintenance calories 2,400 kcal/day Daily calorie target 1,850 kcal/day · Daily deficit 550 kcal/day · Weekly weight change 0.50 kg · Total weight change 10.00 kg
General background references
Disclaimer
These calculators are for general information only and are not a medical device, a diagnosis or a treatment plan. Reference ranges describe populations, not individuals, and do not account for pregnancy, medication, disability or athletic training. Discuss your own situation with a qualified healthcare professional.
Implementation source
This record describes the implementation used by this page. It is not independent validation. External references, when available, support only the stated formula or definition; estimates and custom rules retain their own assumptions.
Formula and variables
D = (W₀ − W₁)·7700 ÷ (7t); C = C_m − D
- D
- Daily calorie deficit
- W₀
- Current weight, kg
- W₁
- Target weight, kg
- t
- Timeframe, weeks
- C
- Daily calorie target
- C_m
- Maintenance calories
This is static arithmetic, not a dynamic weight-response model: it assumes 7,700 kcal per kg and fixed maintenance calories. Actual energy needs and weight change adapt over time; the result is not a personal medical or nutrition recommendation.
Frequently asked questions
How does the 7,700 kcal per kilogram assumption affect the target?
The model multiplies the desired weight change by 7,700 kcal per kilogram and divides by the number of days. Going from 85 to 75 kg over 20 weeks produces a 550 kcal daily deficit; over 10 weeks it produces 1,100 kcal daily. Actual weight change is dynamic and will not necessarily follow this fixed conversion. The tool does not assess whether a calorie target is appropriate for an individual.