• Question: how big are sperm cells?

    Asked by decy to Adam, Catherine, Karen, Leila, Nazim on 10 Mar 2012.
    • Photo: Nazim Bharmal

      Nazim Bharmal answered on 10 Mar 2012:

      Oooh. I’d guess about 100 lined up would be 1 centimetre long. I think they are quite big actually, compared to blood or skin cells for example. (They have to be so they can swim!)

    • Photo: Adam Stevens

      Adam Stevens answered on 10 Mar 2012:

      Really tiny! They’re about a thousandth of a millimeter across, though their tail is about 10 times as long.

    • Photo: Karen Masters

      Karen Masters answered on 10 Mar 2012:

      This is very far out of my area of scientific expertise – but we often do think about how to explain the scales of things in astronomy. One great tool for that is this Interactive “Scale of the Universe” (link below) which goes from subatomic particles, all the way up to the whole universe. I would guess Sperm are between the scales of the largest virus and the red blood cell, but if I’m honest that’s a total guess!

      http://scaleofuniverse.com/

    • Photo: Leila Battison

      Leila Battison answered on 10 Mar 2012:

      Sperm cells are on average about 5 microns across (including their tail), which is about the same size as our blood cells. That’s five thousandths of a millimetre, and you’d need quite a good microscope to be able to see them. You could fit 400 lined up head to tail across the head of a pin, and there’s on average 40 million of them in every single ejaculate (yes, ejaculate, tee hee).

      Sperm are much much smaller than the female egg, the ovum – about 2% of the size, because they need to be fast swimmers to give them a good chance of fertilising the egg.

      I seem to know a lot about these sorts of things, how weird!

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