The answer is tens of billions of kilometers
A typical human cell with a nucleus contains about two meters of DNA when the molecule is unwound. Multiply that by the roughly tens of trillions of cells in a body, and the total comes to tens of billions of kilometers—hundreds of times the distance between Earth and the Sun.
It is an estimate, not a literal tape measure. Cell counts vary, and not every cell has DNA: mature red blood cells, for example, shed their nuclei. Cells also differ in how much DNA they carry.
How two meters fit inside one cell
DNA is a long, thin molecule, but it does not lie loose in the cell. It winds around protein spools and folds into compact bundles called chromosomes. This packaging keeps the genetic material small enough to fit inside the nucleus, while allowing sections to be opened when the cell needs to read particular genes or copy its DNA before dividing.
The folding is highly organized rather than a simple ball of tangled thread. That organization helps the cell manage a molecule far longer than the nucleus itself and control which stretches are accessible at a given time.
A vast length, divided among tiny packages
The startling total comes from multiplying a modest length per cell by an enormous number of cells. But the DNA is distributed across separate microscopic compartments, not joined into one continuous strand. If gathered and stretched out, it would be an astronomical length; inside the body, it remains folded, protected, and parceled into individual cells.
