How much DNA do humans have?
Answer to the question
How much DNA is there in our cell nuclei?
In humans, there are about 6 billion base pairs in the nucleus of each cell. Why 6 billions and not 3? There are 3 billions base pairs per haploid genome (see ploidy) and therefore 6 billions base pairs for the whole genome. This number may actually further double during specific phases of the cell cycle. Each single cell contains a copy of the whole genome (with a few exception such as red blood cells for example).
So the total number of base pairs in a 10 trillion cells individuals is about $6\cdot 10^9 \cdot 10^{13} = 6\cdot 10^{22}$ base pairs.
Further information for fun
How much DNA in our cells outside of nuclei
Now, in cells there is DNA outside of nuclei. In animals (incl. humans), we have DNA in mitochondria as well. there is of the order of 104104 base pairs per mitochondria (16,569 sites to be accurate) and there are of the order of 104104 mitochondria per cell, that is 108108 base pairs total per cell which is only one order of magnitude below the number of base pairs in the nucleus per cell.
There is therefore an extra $3\cdot 10^8 \cdot 10^{13} = 3\cdot 10^{21}$ base pairs in cells outside the nucleus.
How much DNA in bacteria living in the human body?
Note that by &quot;in the human body&quot;, I also include &quot;in the gut&quot; even though the inside of the guts are typically considered as being the outside our body.
There are about 100 trillions of bacteria in every one of us (this number is a vague approximation; see wiki &gt; Human microbiota). Yes, most of the cells living in us are not our cells but are bacterial cells!
Bacterial genome vary widely but as a gross and almost insulting approximation, let's consider that the average bacterial genome from our microbiome has a genome size of $10^6$ base pairs (note bacteria don't have nuclei or mitochondria).
That means that in our body we have to add to the above numbers $10^6 \cdot 10^{14} = 10^{20}$ base pairs (which is only a hundredth of $10^{22}$).
How much DNA in the viruses in our body?
Let's not forget our virome. Unfortunately, I could not find estimates of the number of viruses (and viroids) in our body.
How much DNA is outside cells and viruses in our body?
Of course, there's plenty of DNA in our body. There's DNA in everything we eat and this DNA end up in our blood stream and in our cells. I failed to find an estimate of how much DNA does that represent.