Size in megabytes is not an indicator of the real file size, jpgs use compression, and compression varies with subject matter and sharpness.
What matters is the pixel dimensions, if they are the same as the original, the image is the same size.
Raw files are 14 bit NEF's. Jpegs are 8 bit compressed files;so will always be smaller.
highest quality my exporst are only around 1.9-2.4MB.
Your mistake is that you think quality can be measured in megabytes of the file. This is incorrect. The megabytes do not tell you anything about the image's quality. You should ignore the megabytes.
To get a high quality export, you should uncheck "Resize to Fit" and set the quality slider about 80. That's all you need to do.
Well, I am not very familiar with all of that. I normally print everything myself and have printed pretty big prints, the quality has always been great. But, I never print from jpegs. The situation is, I took a part time job and the company's lab wants the images at least 3MB. I cannot do that with lightroom., as my images are exporting lower than that (as far as MB are concerned). I am having to export them and then resize them in Photoshop (again I am not very knowledgeable with what is correct this is the only solution I have found so far). This process takes me twice as long, so that is a problem.
And I do not have "Resize to fit checked"
You should tell the lab (who ought to know better) that megabytes are irrelevant.
The pictures should print fine.
I agree with Per Berntsen, this is a meaningless requirement. And stupid too.
However, if you absolutely must get to 3MB because your employer requires it, in Lightroom you would check "Resize to Fit", uncheck "Do Not Enlarge" and then type in some large number of pixels, for example 6000x4000 or whatever works for you. I point out that this will NOT increase the quality of the image, even though it will probably be greater than 3MB, in fact it will lower the quality of your image because now Lightroom has to "make up" pixels to make the image this large.
Lastly, are you 100% sure the requirement is 3 megaBYTES (which makes no sense) and not 3 megaPIXELS (which is a perfectly reasonable requirement)?
OK thanks and it is 3MB.
Sorry I am not making up the rules.
And thanks for clarifying, I have to laugh as I remember when I use to go to the hardware store and they would always sell me nails when I wanted screws. I always wanted the screws but kept calling them nails. It took several years before someone made me aware of my improper grammar!!