deficit calculator

What is a calorie deficit?

A calorie deficit means you consume fewer calories than your body burns in a day. When this happens consistently, your body uses stored energy (mostly body fat, plus some glycogen and water), and your weight trends down over time.

In simple terms:

• Maintenance calories: what you need to stay at roughly the same weight.
• Deficit calories: maintenance minus a planned amount.
• Target intake: the daily calories you aim to eat for fat loss.

How this deficit calculator works

1) Basal Metabolic Rate (BMR)

Your BMR is the estimated number of calories your body needs at complete rest. This calculator uses the well-known Mifflin-St Jeor formula:

• Men: BMR = (10 × weight kg) + (6.25 × height cm) − (5 × age) + 5
• Women: BMR = (10 × weight kg) + (6.25 × height cm) − (5 × age) − 161

2) Total Daily Energy Expenditure (TDEE)

TDEE is your BMR multiplied by activity level. It includes movement, workouts, and daily living. This gives a practical estimate of maintenance calories.

3) Deficit based on desired rate of loss

Roughly, 1 kg of body fat corresponds to about 7,700 kcal. So if you target 0.5 kg/week, your daily deficit is approximately:

(0.5 × 7,700) ÷ 7 ≈ 550 kcal/day

Your target intake is then:

Target Calories = TDEE − Daily Deficit

How big should your deficit be?

Most people do best with a moderate deficit. Faster is not always better. Too aggressive can cause fatigue, hunger, poor training performance, and muscle loss risk.

• 0.25 kg/week: easiest to sustain, ideal if you are already lean.
• 0.5 kg/week: excellent starting point for many adults.
• 0.75 kg/week: useful for motivated individuals with higher starting body fat.
• 1.0 kg/week: generally short-term and only if recovery, sleep, and protein are well managed.

What to eat while in a calorie deficit

Prioritize protein

Protein helps preserve lean mass and improves satiety. A practical target for dieting is often around 1.6–2.2 g per kg of body weight per day.

Keep dietary fat adequate

Fat supports hormones, absorption of fat-soluble vitamins, and general health. Going too low often backfires.

Use carbs strategically

After protein and fat are set, fill remaining calories with carbohydrates. This can support training output, mood, and adherence.

Common reasons progress stalls

• Underestimating portion sizes.
• Weekend overeating that erases weekday deficits.
• Reduced daily movement (NEAT) as diet fatigue increases.
• Poor sleep and high stress leading to cravings and water retention.
• Expecting scale weight to drop linearly every day.

How to adjust your deficit over time

Track your average weight (not one single weigh-in). If your 2–3 week trend is not moving:

• Reduce calories by 100–200/day, or
• Add 1,500–3,000 daily steps, or
• Add one short conditioning session per week.

Make small changes, then reassess after another 2–3 weeks.

FAQ

Is this calculator perfectly accurate?

No calculator is perfect because metabolism and activity vary person to person. Use this as a smart starting estimate, then adjust based on real-world results.

Can I lose fat without counting calories?

Yes. But calorie tracking (at least briefly) can teach portion awareness and often speeds up results.

Do I need cardio?

Not mandatory, but helpful. Resistance training plus daily movement is a strong baseline. Cardio is a useful tool to widen your energy gap without slashing food too hard.

Final takeaway

A good deficit plan is one you can follow consistently. Start moderate, hit protein, train hard, sleep well, and make small adjustments using trend data. Use the calculator above to set your initial target, then refine it as your body responds.