Thanks for the reply.
My sketch size is less than 30720 and I get the error. As far as I can tell, using trial and error, my upload fails if size greater than 28672 bytes.
Are all UNO boards, including clones, use the 512 byte optiboot bootloader?
How about chips sold by adafruit which claims to have their own bootloader, does that take up 2k or 512 bytes?