# What is the capacity of the human brain?

What would a reasonable estimate be of the data capacity of the human brain expressed in bytes?

## 1 Answer

Paul Reber, professor of psychology at Northwestern University, stated that

The human brain consists of about one billion neurons. Each neuron forms about 1,000 connections to other neurons, amounting to more than a trillion connections. If each neuron could only help store a single memory, running out of space would be a problem. You might have only a few gigabytes of storage space, similar to the space in an iPod or a USB flash drive. Yet neurons combine so that each one helps with many memories at a time, exponentially increasing the brain’s memory storage capacity to something closer to around 2.5 petabytes.

1PB = 1,000,000,000,000,000 B = 1015 bytes = 1000 TB (terabytes).
1TB = 1,000,000,000,000 bytes = 1012 bytes = 1000 GB (gigabytes). So
2.5PB = 2.5 million gigabytes

For comparison, if your brain worked like a digital video recorder in a television, 2.5 petabytes would be enough to hold three million hours of TV shows. You would have to leave the TV running continuously for more than 300 years to use up all that storage.

The same article states that although it is stated that the brain is capable of storing around 2.5PB of information,

The brain’s exact storage capacity for memories is difficult to calculate. First, we do not know how to measure the size of a memory. Second, certain memories involve more details and thus take up more space; other memories are forgotten and thus free up space. Additionally, some information is just not worth remembering in the first place.

• Sounds like pseudoscience to me Jun 10, 2017 at 19:43
• @Charlie A lot of assumptions we cannot get proof, but they are made explicit, so I believe it is fine and 100% in line with what the OP requested. Oct 16, 2018 at 8:18
• All of these "capacity estimates" are bunk. It could easily be hundreds or thousands of orders of magnitude off. The brain does not store data using bits and bytes, and although information theory does allow us to measure brain capacity in bits, actually calculating that is far beyond us. After all, you're saying that the brain is capable of existing in 2^(2.5×10^18×8) functionally distinct states, i.e. that it can be described in 2.5×10^18×8 bits. RAM only ever contains 1s and 0s, so there's a very, very specific number of functional states a computer can exist in. The brain is far different. Jun 16, 2019 at 2:27
• "one billion neurons” I think that’s a huge understatement I am sure its more like 86 billion. Sep 7 at 12:01