Are you underweight?
By the WHO adult classification, a BMI under 18.5 is underweight. At 160 cm (5′3″), the healthy range starts at 18.5 × 1.6² ≈ 47.4 kg (104 lb). If you have lost weight recently without trying, are eating less, or have fatigue or digestive problems, see a doctor before you start calculating.
Your gain target
Example: woman, 28, 160 cm, 46 kg (BMI 18.0). Mifflin BMR about 1,159 kcal.
| Activity level | TDEE | +250 kcal | +500 kcal |
|---|---|---|---|
| Sedentary | 1,391 | 1,641 | 1,891 |
| Light | 1,594 | 1,844 | 2,094 |
| Moderate | 1,796 | 2,046 | 2,296 |
Start at +250 kcal and adjust after 2–3 weeks of trend. Using the 7,700 kcal per kg approximation, +250 kcal a day is about 0.2 kg a week and +500 about 0.45 kg. Pairing it with strength training and enough protein (protein in grams) means more of the gain is muscle.
Eating more without forcing it
- Add one snack rather than making every meal bigger: milk, nuts, yogurt or a banana.
- A drizzle of oil or a nut-based sauce on rice or pasta adds calories without adding volume (fat is 9 kcal per gram).
- Lots of liquid right before a meal fills you up first, so save drinks for after.
Setting it up in the app
Check BMI and healthy weight range
Near the bottom of the Calculator tab in Calorie Calculator, the "Body Mass Index (BMI)" card shows your BMI class (Underweight, Normal, Overweight, Obese) and the healthy weight range for your height.
Set the goal to gain
Under "Goal", choose Gain mild (+250) or Gain fast (+500); Daily target calories and the estimated weekly change update. Enter a goal weight and date to see how many extra calories a day that plan needs.
Fill the day with the Diet ring
The ring on the Diet tab shows how much is left to reach today’s target, so you know how big a snack to add.
Sample food names in the screenshots are in Korean; the app itself runs in English.
FAQ
Can I hit the number with fast food?
The calories add up, but protein and micronutrients tend to fall short. Try adding snacks to your normal meals first.
When will I start to see it?
The first few days swing with food and water weight. Watch whether the moving average climbs over 2–3 weeks. If you chose a low activity level, try one step up.
Sources: WHO, BMI classification
Calorie Calculator: BMR TDEE
No sign-up, and your body data and logs stay on your phone. Free on Android.