This weight gain calculator finds the daily calorie surplus needed to gain a target amount of weight by a chosen date, using the guideline that about 7,700 kcal builds 1 kg. Enter your goal above.
Formula
Daily surplus = (kg to gain × 7,700) ÷ days
Example
Gain 5 kg in 60 days: surplus = (5 × 7,700) ÷ 60 ≈ 642 kcal/day above maintenance.
Healthy gain pairs the surplus with strength training so more of it is muscle. Some medical conditions and medications also affect weight — discuss unexplained changes with a clinician.
Important
This tool is for general educational purposes only and is not medical advice, diagnosis, or treatment. It does not replace evaluation by a qualified healthcare professional — consult one for any health concern. Last updated: August 2026.
Frequently Asked Questions
How do I calculate calories to gain weight?
Multiply the kilograms you want to gain by about 7,700, then divide by your number of days, and add that surplus to your maintenance calories.
How fast can I safely gain weight?
Often about 0.25-0.5 kg per week for lean gains; faster adds more fat. Pair the surplus with resistance training.
Why am I gaining weight without eating more?
Medications, hormones, fluid, and health conditions can affect weight. If gain is unexplained, see a healthcare provider.