Calorie Deficit Calculator
A calorie deficit means eating fewer calories than your body burns, and it’s the basic mechanism behind weight loss. Enter your details above and the calculator will estimate your BMR, your TDEE, and a moderate daily calorie target.
Please read this first: the result is a starting estimate based on standard formulas, not a medical or nutrition plan. If you are pregnant or breastfeeding, under 18, have a history of disordered eating, or have a medical condition, talk to a doctor or registered dietitian before cutting calories.
Calorie Deficit Calculator
Your Personal Caloric Targets
BMR vs. TDEE: What’s the Difference?
BMR (Basal Metabolic Rate) is what your body burns at complete rest, just to keep you alive: breathing, circulation, cell repair. Even if you stayed in bed all day, you’d still burn roughly this much.
TDEE (Total Daily Energy Expenditure) is BMR plus everything else: walking, working, exercise, even digesting food. It’s the number that matters for weight loss, because it’s roughly the amount you eat to stay the same weight.
TDEE = BMR × Activity Multiplier
How This Calculator Works
This calculator estimates BMR with the Mifflin-St Jeor equation, which is widely considered more accurate for most people than the older Harris-Benedict formula.
- Men: BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age) + 5
- Women: BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age) − 161
Then BMR is multiplied by an activity factor:
| Activity level | Multiplier |
|---|---|
| Sedentary (desk job, little exercise) | 1.2 |
| Lightly active (light exercise 1–3 days/week) | 1.375 |
| Moderately active (exercise 3–5 days/week) | 1.55 |
| Very active (hard exercise 6–7 days/week) | 1.725 |
These multipliers are averages, not measurements. People most often get the wrong result by picking an activity level that’s too high. If you’re unsure, choose the lower one.
Worked Example
Take a 30-year-old woman who is 70 kg, 165 cm tall, and lightly active.
- BMR = (10 × 70) + (6.25 × 165) − (5 × 30) − 161 = 700 + 1,031 − 150 − 161 ≈ 1,420 calories
- TDEE = 1,420 × 1.375 ≈ 1,950 calories
- With a 500-calorie deficit, her daily target is 1,950 − 500 ≈ 1,450 calories
Now a 35-year-old man who is 85 kg, 178 cm, and lightly active.
- BMR = 850 + 1,112 − 175 + 5 ≈ 1,793 calories
- TDEE = 1,793 × 1.375 ≈ 2,465 calories
- With a 500-calorie deficit, his target is about 1,965 calories
These are illustrations of the math only. Your own numbers will differ.
What’s a Safe Calorie Deficit?
A deficit of 500 to 750 calories per day is the commonly recommended range for steady weight loss, which works out to roughly 1 to 1.5 pounds (0.5 to 0.7 kg) per week. It isn’t the fastest option, but it’s the pace most associated with weight loss people can actually keep up.
Minimum calorie floors. General guidelines often cite about 1,200 calories a day for women and 1,500 for men as levels not to go below without medical supervision. These are not targets. If your calculated target is below the floor, the safer move is a smaller deficit, not a stricter diet.
Deficit size matters too. If your TDEE is low, a 500-calorie cut is a big percentage of what you eat. In that case choose a smaller deficit (for example 250 to 300 calories) and be patient.
Signs Your Deficit Is Too Aggressive
- Constant tiredness, dizziness or poor sleep
- Feeling cold, or noticeable hair loss
- Strength dropping quickly in your workouts
- Strong, constant hunger or preoccupation with food
- Missed or irregular periods
If you notice these, eat more and speak to a healthcare professional. Faster is not better here: a deficit that is too large often leads to muscle loss and to regaining the weight later.
How the “3,500 Calorie Rule” Works (and Where It Fails)
The old rule says about 3,500 calories equal one pound of body fat, so a 500-calorie daily deficit (500 × 7 = 3,500) should give about a pound a week. It’s a handy rough guide, but real life is bumpier:
- Your TDEE drops as you lose weight. A smaller body burns fewer calories, so the same deficit slowly produces less loss.
- Water weight hides progress. Salt, hormones and carbs can move the scale by a pound or more in a day without any change in fat.
- Everyday movement changes. When people eat less, they often move less without noticing it.
Judge your progress by the trend over two to four weeks, not by one morning’s weigh-in.
Tips to Make a Deficit Easier
- Prioritize protein and fibre to stay fuller.
- Include some strength training to help keep muscle while you lose fat.
- Sleep enough, since poor sleep makes hunger harder to manage.
- Re-run the calculator every 5 kg (10 lb) or so, because your TDEE changes as you lose weight.
Frequently Asked Questions
What is a calorie deficit?
It’s eating consistently fewer calories than you burn, so your body uses stored energy to make up the difference.
Is 1,500 calories a day a deficit?
It depends on your TDEE. For someone with a low TDEE it may be close to maintenance, while for someone with a high TDEE it may be a large deficit. It is also near the commonly cited minimum for men, so don’t go lower without medical advice.
Is a 250-calorie deficit enough?
Yes, it works, only slowly: roughly half a pound a week by the simple estimate. A smaller deficit is often easier to stick to.
Why am I not losing weight in a deficit?
Common reasons are an overestimated activity level, untracked calories, or water retention hiding fat loss. If a consistent deficit shows no result after several weeks, talk to a doctor or dietitian rather than cutting more.
Can I use this while pregnant or breastfeeding?
No. Calorie needs change a lot during pregnancy and breastfeeding, so follow your healthcare provider’s advice.
How accurate is this calculator?
It’s a reasonable estimate for most healthy adults, but every body is different. Use it as a starting point and adjust based on your results over a few weeks.
This page is for general education and isn’t medical or nutrition advice. If you have a health condition or a history of disordered eating, please consult a doctor or registered dietitian.