Try du to summarize disk usage:
du -csh *.jpg
Output (for example):
8.0K sane-logo.jpg
16K sane-umax-advanced.jpg
28K sane-umax-histogram.jpg
24K sane-umax.jpg
16K sane-umax-standard.jpg
4.0K sane-umax-text2.jpg
4.0K sane-umax-text4.jpg
4.0K sane-umax-text.jpg
104K total
du does not summarize the size of the files but summarizes the size of the used blocks in the file system. If a file has a size of 13K and the file system uses a block size of 4K, then 16K is shown for this file.