Calorie Deficit Calculator

About this tool

The Calorie Deficit Calculator turns a target weight-loss rate into a concrete daily calorie target and a weekly deficit. It accepts TDEE directly or computes it from age, sex, height, weight, and activity using Mifflin-St Jeor. The math anchors on the standard energy balance: ~7,700 kcal/kg (3,500 kcal/lb) of body mass change. Safety guardrails warn when your loss rate exceeds ~1 kg/week (2 lb/week), which evidence-based guidelines flag as unsustainable, and when your daily intake drops below conventional floors (~1,500 kcal men, ~1,200 kcal women). Sustainable fat loss is 0.5-1% of body weight per week, paired with adequate protein and resistance training to preserve lean mass. This calculator is for educational purposes only and is not a substitute for professional medical advice. Always consult a qualified healthcare provider before making decisions about your health.

Why use it

• Combines TDEE calculation and deficit math in one place — no juggling separate calculators.

• Built-in safety guardrails warn when targets exceed sustainable rates or drop below safe floors.

• Mifflin-St Jeor BMR plus standard activity multipliers — the most accurate widely-used equation.

• Project total timeline in weeks when total weight to lose is provided.

• Imperial or metric units throughout, with rate auto-switching.

• Privacy-first: your weight, height, age, and goals never leave your browser.

How to use

1. Choose 'Auto-compute TDEE' to enter age, sex, weight, height, and activity, OR pick 'I know my TDEE' if you already have a number.
2. Pick your unit system (kg/cm or lb/in) — the rate field switches automatically.
3. Enter a target loss rate per week (typical recommended range: 0.25-1 kg or 0.5-2 lb).
4. Optionally enter the total amount you want to lose to see a projected timeline in weeks.
5. Review the daily calorie target, weekly deficit, and any safety warnings before starting.
6. Track adherence weekly and adjust if real-world weight loss is faster or slower than projected.

When it helps

• Starting a fat-loss phase and needing a concrete daily calorie target.
• Adjusting your deficit when weight loss stalls or accelerates unexpectedly.
• Setting realistic expectations for how long a goal will take.
• Avoiding aggressive deficits that lead to muscle loss or disordered eating patterns.
• Coaching others through goal-setting with evidence-based guardrails.
• Preparing for a competition, photoshoot, or weight class with a structured timeline.

Examples

Tips

• Aim for 0.5-1% of body weight per week — fast enough to see progress, slow enough to keep muscle.
• Eat 1.6-2.2 g of protein per kg of body weight during a deficit to minimize muscle loss.
• Re-check TDEE every 4-6 weeks during a long cut — metabolic adaptation reduces it as you lose mass.
• Take one maintenance week at TDEE every 8-12 weeks to reset hormones and adherence.
• Track 7-day rolling average weight rather than daily numbers to filter out water-weight noise.

Frequently Asked Questions

Glossary

Caloric deficit

A daily intake that is lower than total daily energy expenditure (TDEE), forcing the body to draw on stored energy (mostly fat) for the difference.

TDEE

Total Daily Energy Expenditure — the number of calories you burn in a 24-hour period across BMR, food digestion, NEAT, and exercise.

BMR

Basal Metabolic Rate — the calories your body burns at complete rest to keep organs running. Typically 60-75% of TDEE.

Metabolic adaptation

Reduction in TDEE during prolonged caloric deficit beyond what mass loss alone predicts; driven by hormone shifts and reduced NEAT. Roughly 100-300 kcal/day for most cutters.

NEAT

Non-Exercise Activity Thermogenesis — calories burned through fidgeting, posture, and unstructured daily movement; declines automatically during a deficit.

Refeed / diet break

Planned periods at maintenance calories during a long cut to reduce adaptation and improve adherence; typically 1-2 weeks every 8-12 weeks of dieting.