Megapixels, (MP's), the sensor size and Megabytes, (MB's) the image file size

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I have just bought a couple of cameras, a Leica Q and a Nikon Zf - both have 24 MP sensors

Shooting both in RAW and then downloading the files into Lightroom one produces an image with a file size of around 43MB's and the other with a file size of around 18 MB's

My D850 with a 45MP sensor seems to produce images with a file size of 50MP's

Difference RAW files???

Can anyone explain this relationship
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I'd guess it would be one having a more efficient compression algorithm.

For example, if both cameras are seeing a block of 10 pixels that are pure black, one may record this as one block, the other may record this as 10x individual pixels.

I don't know the individual systems to give a precise answer but that would be my guess.
I don't know but the first thought that comes to mind in the number of bits per photo site (pixel). e.g. one sensor might use 16 bits per pixel and another 24 bits per pixel giving a bigger file
I believe the files as default are compressed from the Nikon ZF, and if you go further into the menu you can select them as lossless which would give you a bigger file size.
The Nikon ones are NEF the Leica DNG

also the M8 with a 10MP sensor produces DNG files of 10MB
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File compression?
Leica Q doesn't compress the files.
Most likely file compression. My A7III with 24mpx gives around 24MB compressed or 47-48MB without (lossy) compression.
you can convert these "large" uncompressed files in LR

(just reduced the Leica DNG from 40MB to just over 4MB at the click of a mouse!!)

"Lightroom has a feature called Lossy DNG compression, which allows you to reduce the size of your DNG files while maintaining image quality. This compression technique works by removing some of the image data that is considered unnecessary, resulting in smaller file sizes. In addition, the compression is done in a way that is not visible to the naked eye so that you won’t notice any degradation in image quality"

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from what I am reading on the internet the above method would appear to be true - i.e. the compressed file is as good as the original to the naked eye

certainly worth trying on images that you are just saving as a record - i.e. 3 star images for example

Maybe Steven will come along and clarify the method/results
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I'm seeing an average file size of 27-37mb mentioned for the ZF on websites. It's also claimed that most of the working parts are Z62. I dont have either camera to check.
I don't know about Leica and Nikon, but Sony also embed a 2Mb Jpeg 'preview' image in every raw file - if Leica and Nikon do likewise, but have different sized Jpegs, that could add to the difference.
The more I read about this the more interesting it is - when you consider that the Leica M11 with a 60mp sensor is producing 100mb DNG files - and the more I read the more I hear that the human eye (generally) can only resolve 10 pixels per mm - implying that such large files will seldom be needed, (and maybe 24mp is the sweet spot for the majority of prints) - (clearly you can crop part of the M11 image to give you "smaller" files) - please note that in no way am I an expert or giving an expert opinion - all this is new to me