Because you only gave a weight, we assumed a typical 30-year-old woman of 5'5" with a lightly active routine. Height and age change the answer: see the sensitivity table below, then enter your real numbers.
The calculation, step by step
1. Convert to metric
150 lb / 2.205 = 68.0 kg. 5'5" = 65 in x 2.54 = 165.1 cm.
2. BMR (Mifflin-St Jeor)
BMR = 10 x 68.0 + 6.25 x 165.1 - 5 x 30 - 161 = 1,401 calories. That is what the body burns at complete rest. The equation comes from Mifflin et al., Am J Clin Nutr 1990.
3. Multiply by activity (Lightly Active, x 1.375)
1,401 x 1.375 = 1,927 calories. Light exercise 1-3 days/week. This is TDEE, or maintenance calories.
4. Subtract (or add) for your goal
Cut: 1,927 - 500 = 1,427. Gentler cut: 1,927 - 250 = 1,677. The -500 target (1,427) stays above this profile's BMR (1,401), which is the practical floor to stay above.
Deficit and surplus table
| Goal | Calories / day | Expected weekly change |
|---|---|---|
| Lose (-500) | 1,427 | -1 lb / -0.45 kg |
| Lose (-250) | 1,677 | -0.5 lb / -0.23 kg |
| Maintain (0) | 1,927 | 0 lb / 0 kg |
| Gain (+250) | 2,177 | +0.5 lb / +0.23 kg |
Weekly change uses the common rule of thumb of about 3,500 calories per pound (7,700 per kg). It is an approximation: as you lose weight your needs fall, so real long-run change is slower (Hall et al., Lancet 2011). Suggested protein at this weight: about 135 g a day (0.9 g per lb).
If your activity is different
| Activity level | Multiplier | TDEE | Cut (-500) |
|---|---|---|---|
| Sedentary | 1.2 | 1,681 | 1,181 |
| Lightly Active | 1.375 | 1,927 | 1,427 |
| Moderately Active | 1.55 | 2,172 | 1,672 |
| Very Active | 1.725 | 2,417 | 1,917 |
| Extremely Active | 1.9 | 2,662 | 2,162 |
Most people overestimate their activity level. If you sit most of the day and train a few times a week, start from lightly active, not moderately active. Prefer counting steps? Convert steps to calories: at this size, every extra 1,000 steps burns roughly 26 calories, so 10,000 steps a day adds about 130 calories above a 5,000-step day.
How much height and weight matter
| Change | TDEE | Difference |
|---|---|---|
| 140 lb | 1,864 | -63 |
| 150 lb (this example) | 1,927 | - |
| 160 lb | 1,989 | +62 |
| 5'3" tall | 1,883 | -44 |
| 5'7" tall | 1,970 | +43 |
Ten pounds moves maintenance by about 62 calories, and two inches by about 43. Among women the same weight can mean a very different number, which is why a one-line answer to "how many calories should I eat" is only a starting point. Know your body fat? The calculator switches to Katch-McArdle, and the AI body fat estimator can give you the input from a photo.
What to do with this number
- Eat at 1,927 for two to three weeks and weigh yourself most mornings. Flat trend means the estimate is about right.
- To lose, start at 1,677 to 1,427. To gain slowly, try 2,177.
- Split it into protein, carbs and fat with the macro calculator, or turn it into a meal plan.
- Log it free in the baisics app, with a training plan built around these numbers: start free.