Is 1,200 kcal a magic minimum?

It is a practical floor below which nutrient adequacy gets difficult for most adults, not a biological cliff. Very-low-calorie diets require medical supervision.

Can I bank deficits across the week?

Yes; weekly energy balance is what matters. Some people prefer larger weekday deficits with higher weekend intake at the same weekly total.

Does the 7,700 rule account for water weight?

No. It models pure energy balance; short-term scale swings from sodium, carbs and hydration can mask or exaggerate real fat changes.

Health

Calorie Deficit Calculator

What this does

Turn your TDEE into a daily calorie target for fat loss, with expected weekly and monthly progress at your chosen deficit.

Enter your details

Runs in your browser

How to use it

Using the calorie deficit calculator

01
Enter your TDEE
Use the TDEE calculator result, or your empirically tracked maintenance intake.
02
Choose a deficit size
Standard advice favors 500 kcal; large enough to see weekly progress, small enough to sustain.
03
Set your target and track
Eat near the computed target and compare actual scale trends against the projected rate after three weeks.

Good to know

Bigger deficits are not better

Beyond roughly 30% below maintenance, hunger hormones rise, training quality drops and lean-mass losses accelerate. Slower cuts preserve muscle and are dramatically easier to adhere to over months.

Why the scale stalls anyway

Early losses include glycogen-bound water; later, adaptive thermogenesis shrinks true expenditure below predictions. Expect the linear projection to soften; judge progress by the 3-week trend, not daily readings.

Protecting muscle while cutting

Keep protein high (see the protein intake calculator).
Continue resistance training with maintained loads.
Prefer moderate deficits of 15–25% below TDEE.

How it's calculated

The math behind this calculator

Target = TDEE − deficit
Weekly loss ≈ deficit × 7 ÷ 7700 kg

Your daily target is simply maintenance minus the chosen deficit. Progress converts through the energy-density convention that one kilogram of body fat stores approximately 7,700 kcal, so a sustained 500 kcal daily deficit yields roughly half a kilogram of loss per week.

Deficits that would push intake below 1,200 kcal/day are rejected; below that threshold meeting micronutrient needs becomes genuinely difficult without medical supervision.

Assumptions & limitations

One kilogram of body fat ≈ 7,700 kcal (population-average convention).
Linear projection ignores metabolic adaptation and water fluctuations.
Protein intake and resistance training strongly influence how much lost weight is lean mass.

Worked example

Maintaining on 2,500 kcal/day and cutting 500 creates a 2,000 kcal target; about 0.45 kg of expected loss per week, or roughly 1.9 kg per month.

FAQ

Frequently asked questions

Is 1,200 kcal a magic minimum?: It is a practical floor below which nutrient adequacy gets difficult for most adults, not a biological cliff. Very-low-calorie diets require medical supervision.
Can I bank deficits across the week?: Yes; weekly energy balance is what matters. Some people prefer larger weekday deficits with higher weekend intake at the same weekly total.
Does the 7,700 rule account for water weight?: No. It models pure energy balance; short-term scale swings from sodium, carbs and hydration can mask or exaggerate real fat changes.

Keep exploring