Calorie Calculator
How it works
We estimate your maintenance calories (BMR via Mifflin-St Jeor × an activity factor of 1.2–1.9), then apply your goal. About 7,700 calories equals 1 kg of body weight, so losing 0.5 kg a week means eating roughly 550 calories a day below maintenance.
Targets are clamped to a safe minimum (about 1,200 kcal for women, 1,500 for men). If your chosen rate would drop below that, we flag it so you can pick a gentler, more sustainable pace.
Frequently asked questions
How many calories should I eat a day?+
It depends on your body, activity and goal. This calculator estimates your maintenance calories, then adds or subtracts calories for your chosen weekly rate of loss or gain. Enter your details above to see your number.
How is my calorie target calculated?+
We estimate your maintenance calories (BMR via Mifflin-St Jeor × an activity factor), then apply your goal: about 7,700 calories equals 1 kg of body weight, so losing 0.5 kg a week means a deficit of roughly 550 calories a day.
How big should a calorie deficit be?+
A deficit of 300–550 calories a day is sustainable for most people and loses roughly 0.25–0.5 kg per week. Aggressive deficits are harder to stick to and risk muscle loss.
Why is there a minimum calorie limit?+
Eating too little is unsafe and backfires. We clamp targets to about 1,200 calories a day for women and 1,500 for men, and warn you if your chosen rate would drop below that.
Do I have to count calories to hit this target?+
No. Flun's AI logs your meals from a photo, your voice, or a sentence and tracks the total for you — so you hit the target without manual counting.