[Jonty30]

The brain uses about 20% of your body’s energy usage.

Using a conversion conversion chart, from calories to wattage, 300 calories = about 0.3489 watts/day. So, the average brain uses around 0.3489 watts/day.

The human body is amazingly efficient.

[Secret Agent Man]

3 minutes air
3 hours freezing exposure
3 days water
3 weeks food

[I-ambush]

I was thinking of the Matrix movies

[alexander_busek]

Using a conversion conversion chart, from calories to wattage, 300 calories = about 0.3489 watts/day. So, the average brain uses around 0.3489 watts/day.

A watt is a unit of POWER. A watt-hour is a unit of ENERGY. (A calorie is a unit of ENERGY. But the figure you cited should actually be expressed in KILOcalories - a common mistake; the food-energy values we all know are actually KILOcalories.)

One watt-hour is equivalent to 859.8 Kcalories. So 300 Kcalories are equivalent to 2.87 watt-hours.

Thus, if the brain consumes 300 kcalories per day, that would be equivalent to 0.287 watt-hours per day.

In short: Your math is faulty, and you are also using incorrect units.

The correct figure is: The average human brain - when at rest - consumes approx. 287 watt-hours per day.

The amount of energy the brain consumes when actively thinking is not much greater: That's because most of the brain's energy output serves merely to keep approx. 3 lbs of living tissue warm and alive.

Regards,