Calorie Deficit Calculator

How the deficit is calculated

Changing weight comes down to energy balance. This calculator first estimates your maintenance calories, or TDEE, using the Mifflin-St Jeor equation multiplied by an activity factor. It then works out the total energy gap for your goal. Body tissue stores roughly 7,700 calories per kilogram (about 3,500 per pound), so the energy to change is weight change × 7,700. Spreading that over your chosen number of days gives the daily adjustment.

Your daily target is then TDEE − daily deficit for weight loss, or TDEE + daily surplus for weight gain. For example, to lose 7 kg in 10 weeks you need about 53,900 calories of deficit over 70 days, or roughly 770 fewer calories per day than maintenance. The page recalculates instantly as you change any input.

Choosing a sustainable rate

The faster you want to change weight, the larger the daily deficit or surplus required. Common guidance is to aim for about 0.25 to 1 kilogram (0.5 to 2 pounds) per week. Going faster often means very low calorie targets that are hard to sustain, can cost muscle, and may leave you under- fueled. The calculator flags aggressive rates and will not suggest dropping below a sensible floor, because extremely low intakes can be unsafe without supervision.

Use it as a plan, with a health note

Treat the target as a starting plan and check it against real results over two to three weeks, adjusting if the scale or your energy says so. Protein, strength training, sleep and consistency all affect how much of any change is fat versus muscle. This page is for general information only and is not medical or nutritional advice; talk to a doctor or dietitian before starting an aggressive diet. All calculations run locally in your browser and nothing is uploaded.