How many nerve synapses are in the human brain?
Estimates vary, but a generally agreed figure is 1 quadrillion (
This figure is based on an estimate of 100 billion neurons, each with a average of 10,000 synapses.
The reference below uses an estimate of 86 billion neurons, with only hundreds to thousands of synapses per neuron. This comes out as 0.15 quadrillion synapses.
It is also important to note that the number of synapses vary during life - rising during the first year of life, before an extensive period of synaptic pruning. This pruning is actually a good thing, helping to strengthen and reinforce important connections.