What is a Calorie Deficit? (And How to Calculate One Safely)

A calorie deficit is the single requirement for weight loss — no exceptions. Whether you go keto, vegan, or carnivore, if you lose weight, you were in a deficit. Here’s how to calculate one that’s sustainable and safe.

The basic equation

Calorie Deficit = TDEE − Calories Consumed

Where:
  TDEE = Total Daily Energy Expenditure (calories you burn in a day)
  1 kg of body fat ≈ 7,700 calories
  1 lb of body fat ≈ 3,500 calories

To lose 0.5 kg per week, you need a daily deficit of about 550 calories.

How to find your TDEE

TDEE = BMR × Activity Factor

Using Mifflin–St Jeor:

Male BMR:   10 × weight(kg) + 6.25 × height(cm) − 5 × age + 5
Female BMR: 10 × weight(kg) + 6.25 × height(cm) − 5 × age − 161

Activity multipliers:
  Sedentary:    ×1.2
  Light active: ×1.375
  Moderate:     ×1.55
  Very active:  ×1.725

Worked example

Female, 30 years old, 70 kg, 165 cm, lightly active. Goal: lose 0.5 kg/week.

BMR = 10(70) + 6.25(165) − 5(30) − 161
    = 700 + 1031.25 − 150 − 161 = 1420 kcal

TDEE = 1420 × 1.375 = 1953 kcal/day

Target intake = 1953 − 550 = ~1400 kcal/day

Safe deficit ranges

Deficit size	Weekly loss	Risk level
250–350 kcal/day	~0.25–0.35 kg	Very low — sustainable long-term
500–550 kcal/day	~0.5 kg	Moderate — standard recommendation
750–1000 kcal/day	~0.75–1 kg	High — only for obese individuals under medical supervision

Never eat below your BMR. Going too low triggers metabolic adaptation, muscle loss, hormonal disruption, and binge cycles.

When to use a calorie deficit

• You have a clear weight loss goal with a timeline
• You’ve plateaued and need to recalculate (TDEE drops as you lose weight)
• You want to do a short “cut” phase while preserving muscle
• You’re tracking food intake and want a concrete daily number

Tips for staying in deficit without misery

• Prioritize protein (1.6–2.2 g/kg) to preserve muscle and stay full
• Eat high-volume, low-calorie foods: vegetables, soups, berries
• Don’t drink your calories — liquid calories don’t register as filling
• Take diet breaks (eat at TDEE for 1–2 weeks every 8–12 weeks)
• Track for 2 weeks, then adjust — formulas are estimates, not gospel

Use OurDailyCalc’s calorie calculator to get your personal TDEE and deficit targets based on your goal weight and timeline.

TL;DR

• Calorie deficit = TDEE minus food intake
• 550 kcal/day deficit ≈ 0.5 kg lost per week
• Never eat below your BMR
• Recalculate every 5–10 kg lost (TDEE decreases)
• Protein and diet breaks prevent metabolic adaptation