Calorie Deficit Calculator
Find out exactly how many calories you need to cut each day to reach your goal weight — with safety guidance included.
Your Details
Daily Calorie Deficit
Eat this many fewer calories than your maintenance to hit your goal.
Target Daily Intake
1,671
kcal/day to eat
Your Maintenance (TDEE)
2,405
kcal/day to maintain
Weekly Loss
0.67 kg
0.83% of body weight
Total to Lose
8.0 kg
61,600 kcal burn total
moderate pace
Moderate pace. Sustainable for most people if protein intake and sleep are prioritised.
How we got there
- BMR (Mifflin-St Jeor)1,749 kcal
- TDEE (BMR × activity)2,405 kcal
- Total deficit needed61,600 kcal
- Split over 84 days733 kcal/day
About the Calorie Deficit Calculator
A calorie deficit is the state of eating fewer calories than your body burns in a day. When this happens, your body makes up the energy gap by tapping into stored fat — which is how weight loss actually works at a biological level. This calculator tells you exactly how big that gap needs to be to reach your goal weight by your target date.
We use the widely-trusted Mifflin-St Jeor equation to estimate your Basal Metabolic Rate (BMR) — the calories you'd burn doing nothing — then multiply by an activity factor to get your Total Daily Energy Expenditure (TDEE). The difference between your TDEE and your target intake is your deficit.
The math is based on the well-established approximation that 1 kg of body fat ≈ 7,700 kcal (or 1 lb ≈ 3,500 kcal). Real-world weight loss varies with muscle mass, water balance, and metabolic adaptation, but this formula remains the most reliable starting point used by dietitians worldwide.
How to Use the Calorie Deficit Calculator
Pick your units
Switch between metric (kg, cm) and imperial (lb, ft/in) — all inputs update automatically.
Enter your body stats
Age, sex, and height are used to calculate your BMR accurately using the Mifflin-St Jeor formula.
Set your goal & timeframe
Enter your current weight, goal weight, and how many weeks you want to take to get there.
Pick activity level
Be honest — choosing a level too high means your deficit will be smaller than it should be and progress will stall.
Read your daily deficit
Results update instantly. Your target daily intake is the number of calories you should actually eat each day.
Check the safety banner
If the plan is too aggressive, extend your timeframe — slower loss is easier to sustain and better preserves muscle.
Common Use Cases
Summer Body Prep
Plan a realistic cut 3–4 months before an event so you can maintain muscle and avoid rebound weight gain.
Post-Holiday Reset
Lose 2–4 kg gained over the holidays at a gentle, sustainable pace without crash dieting.
Medical Weight Loss
Use alongside your GP or dietitian to set a data-driven calorie target for managed, doctor-supervised weight loss.
Athletic Weight Cut
Combat sports, weight-class events, and jockey clubs — calculate a precise deficit to hit competition weight safely.
Body Recomposition
Combine a mild deficit with strength training and high protein intake to lose fat while maintaining muscle.
Tracking Progress
Recalculate every 4–6 weeks as your weight drops — your TDEE falls too, so the deficit needs to be reset.
Frequently Asked Questions
Everything you need to know about calorie deficits
How big should my calorie deficit be?
For most people, a 300–500 kcal/day deficit is sustainable and loses roughly 0.3–0.5 kg (0.7–1 lb) per week. Deficits over 1,000 kcal/day often lead to muscle loss, hunger, and rebound.
What's the minimum calories I should eat?
A widely-cited floor is 1,200 kcal/day for women and 1,500 kcal/day for men. Eating below these for long periods can cause nutrient deficiencies and metabolic slowdown.
How accurate is the 3,500 kcal per pound rule?
It's a solid approximation based on the energy density of body fat, but individual results vary. Water retention, glycogen, and metabolic adaptation mean actual loss might be a bit slower or faster.
Why did my weight loss stall?
As you lose weight, your TDEE drops because a smaller body burns fewer calories. Recalculate your deficit every 4–6 weeks using your new weight to keep progress steady.
Can I lose weight without counting calories?
Yes — whole-food eating, protein at every meal, and activity increases all indirectly create a deficit. But knowing the rough number helps you spot if you're stuck at maintenance by accident.
Should I factor in exercise calories?
Your TDEE already includes exercise via the activity multiplier. Adding exercise calories back on top of your intake often double-counts and kills the deficit — leave them in the TDEE.
How much protein do I need while in a deficit?
Most research supports 1.6–2.2 g per kg of body weight to preserve muscle during fat loss. A 70 kg person would target roughly 112–154 g of protein per day.
Is this calculator free and private?
Yes. Everything runs in your browser — no sign-up, no tracking of your numbers, no server ever sees your inputs. Safe to use on any device.