Eggs are a powerhouse of protein and nutrients. They are low in calories and can be easily added to many dishes. If you want to know how many calories in a boiled egg?, then a hard-boiled egg contains almost 77 calories, 0.6 grams of carbs, 6.3 grams of protein, 2 grams of monounsaturated fat and 5.3 grams total fat. These eggs also offer many important nutrients such as vitamin D, calcium, zinc and all of the B vitamins. These are particularly excellent sources of vitamin B2 (riboflavin) and vitamin B12.