Is there any database or resource available for finding the legths(bp) of all genes in Homo sapiens?
Eg: Gene Symbol and Length of the gene.
This sounds like something you could easily accomplish by downloading gene data from the UCSC Table Browser and then subtracting end vs start columns.
Would be valuable if you try to find the solution yourself and post what you tried in case it doesn't work. With just an open question people will be less likely to help you. Bioinformatics is not about asking questions on Biostars, it's about doing the struggling yourself. If you can't find a solution after a while, then you can consider to ask questions.
It's of course quicker to just drop the question here, but the reward and learning is far better for everything you fix on your own.
calculating the total length of cDNA for a given gene and links/answers contained within.