Planning

Calorie Deficit Calculator

Estimate required calorie deficit and timeline pacing for a bodyweight change target.

To lose 7.0 kg in 16 weeks, you need a daily deficit of 481 kcal — eating 1,919 kcal/day. That's 0.44 kg per week, reaching your target by July 30, 2026.

Deficit Plan

Daily deficit

481 kcal

Target intake

1,919 kcal/day

Weekly rate

0.44 kg/week

Target date

July 30, 2026

Projected Weight Path

Linear projection from 85 kg to 78 kg over 16 weeks.

StartW8W16

Projected bodyweight

78 kg

Plan macros at 1,919 kcal →Protein for cutting →

Make tracking accurate

Etekcity Food Scale

Precise digital scale for portion control

→

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Energy model: 7,700 kcal ≈ 1 kg body mass (planning approximation).

How to use it

Run the TDEE Calculator first to establish your maintenance calories, then enter that number here along with your weight-loss goal and timeline.
A 500-calorie daily deficit theoretically produces 1 lb/week loss (3,500 cal = 1 lb fat). In practice expect 0.6–0.8 lb/week average due to water fluctuation and metabolic adaptation.
Cap your deficit at 25% of TDEE to preserve lean mass. For a 2,200 TDEE, max sustainable deficit is 550 calories/day. Exceeding this accelerates muscle protein breakdown.
If the scale stalls for 3+ weeks, do NOT simply cut more calories — first recalculate TDEE at your current (lower) body weight. A 10 lb loss typically lowers TDEE by 50–100 calories.
Plan diet breaks: 1–2 weeks at maintenance calories every 6–8 weeks during a sustained cut partially reverses metabolic adaptation and significantly improves long-term adherence.

AI Integrations

Contract, discovery endpoints, and developer notes for agent use.

Always available for agents

Tool contract JSON

https://aifithub.io/contracts/calorie-deficit-calculator.json

Stable input and output contract for this exact tool.

Human review

People can use the browser page to sense-check outputs and charts, but agents should still execute against the contract and discovery endpoints.

/agent-tools.json - machine-readable tool index.
/llms.txt - human-readable model discovery guide.
/.well-known/webmcp.json - WebMCP capabilities manifest.
/.well-known/ai-plugin.json - plugin-style discovery manifest.

{
  "tool": "calorie_deficit",
  "current_weight_kg": 85,
  "target_weight_kg": 75,
  "weeks": 20,
  "activity_level": "moderate"
}

Open tool contract JSON Open AI integrations guide

Expand developer notes

Agent playbook

Resolve Calorie Deficit Calculator from /agent-tools.json and open its contract before execution.
Validate inputs against the contract schema instead of scraping labels from the page UI.
Open the browser page only when a person wants to review charts, assumptions, or related tools.

Agent FAQ

Should ChatGPT, Claude, or another agent click through the UI?

No. Start with /agent-tools.json, then follow the tool's contract URL. The page UI is for human review, not parameter discovery.

When do tools show Quick and Advanced?

Every tool opens in Quick Start first. Advanced Controls keeps the same scenario, reveals more assumptions or diagnostics, and every tool keeps AI integrations inline below the instructions.

When should an agent still open the browser page?

Open it when a human wants to sense-check the output, review the chart, or keep exploring related tools after the calculation finishes.

Questions people usually ask

How large a deficit should I use to lose fat without losing muscle?

Research supports 300-500 calories below TDEE for most people. This yields 0.5-1 lb weekly loss. Deficits exceeding 25% of TDEE accelerate muscle protein breakdown — a 150 lb person should not exceed ~500-600 calorie daily deficit. Protein intake of 0.8-1g per lb of body weight is the most important muscle-preservation factor.

Why did I stop losing weight on the same deficit?

Three reasons: (1) Adaptive thermogenesis — metabolism slows by 5-15% during sustained restriction. (2) Weight loss itself reduces TDEE — lighter bodies burn fewer calories. (3) Food tracking drift — portion accuracy decreases over time. Recalculate your deficit based on current weight and consider a 1-2 week diet break at maintenance.

Is it safe to eat 1200 calories a day?

1200 calories is a minimum threshold commonly cited, but adequacy depends on body size. A 130 lb, 5 foot 4 inch lightly active woman might have a TDEE around 1700 calories — a 500 calorie deficit brings her to 1200, which is adequate. A larger person eating 1200 calories would be in an extreme deficit (40%+) risking muscle loss, fatigue, and nutrient deficiencies.

Related Resources

Learn the decision before you act

Every link here is tied directly to Calorie Deficit Calculator. Use the explanation, formula, examples, and benchmarks to pressure-test the calculator output from first principles.

Browse all 37 resources

Guides · 7 Checklists · 3 Comparisons · 2 Learn · 2 Tips · 7

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Guide

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How to Break a Calorie Deficit Plateau (5 Fixes)

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Guide

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How to Calculate Your TDEE for Any Fitness Goal

Calculate your TDEE using 4 research-backed formulas. Learn which formula is most accurate for your body, why most people overestimate activity level, and how to use TDEE for fat loss or muscle gain.

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Why Your TDEE Drops When You Diet (And What to Do About It)

Metabolic adaptation reduces your TDEE by 5-15% beyond weight loss alone. Learn why it happens, how to detect it, and 4 evidence-based strategies to fight back.

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How to Break a Weight Loss Plateau

Bust through stubborn weight loss plateaus with expert strategies. Learn to optimize your metabolism, refine calorie intake, and adjust your fitness routine for continued progress.

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