But how many calories you need in a day to survive is different from how many calories you usually eat on a day-to-day basis. That's because, in a survival situation, your priority is staying alive until you can better your circumstances and eat more enjoyable foods. Until then, you may not get all the nutrients your body needs to stay in top shape.
Determining the minimum calories needed to survive isn't an exact science due to factors like age, sex and weight. However, it's possible to get close to an ideal range that you can aim for in an SHTF scenario.
Minimum calories needed for survival
Surviving on very few calories for a brief period is possible, but it's not exactly sustainable. For instance, eating fewer than 1,000 calories per day is said to have the same effect physiologically as total starvation.
Experts recommend a much higher calorie level to maintain optimal health. Sedentary adult females should eat 1,800 calories per day, while moderately active ones should eat 2,000 calories. On the other hand, sedentary adult males need about 2,400 calories per day, while an active man needs up to 2,600 calories.
That said, you can survive on 1,200 to 1,500 calories per day if you're in a pinch. However, this amount will only help you barely survive. If your resources are limited, your goal should be to survive on that minimum amount of calories while working towards improving your situation so that you can get back to your normal calorie intake.