Can a short story be turned into a novel? Much like poetry, there is are certain criteria that make a short story just that, a short story. Generally, short stories should run no more than 10,000 words. If it is over that specified word count, and you find yourself unable to slim it down any further, without affecting content, than you may be looking at the beginning of a novel instead of a short story.
How many characters does the story actually need to keep it cohesive and understandable? If you are unable to remove any characters than that is yet another sign that your plot may be too wide to fit that of a short story.
Another area to check is the interwoven theme or themes. Is the story built on multiple themes to make the story complete? Is the theme you have chosen to broad to keep you at the 10,000 word minimum guideline? What about the stories time frame? If the plot is based on years, rather than a brief time period, once again the work is leaning more towards the making of a novel.
How much of a time commitment do you feel comfortable allotting for? Generally writing and completing a novel can take anywhere from 3-7 years. One of the main components in any story is a well-defined plot. Every story needs a central conflict. Take into account the audience you are trying to reach. What will the reader gain from reading your story?
Take all of these items into account when making the leap from short stories to writing a novel. The amount of commitment and time that you will invest is a hefty one. If you are wondering if your story would make a good novel, it never hurts to get others opinions and suggestions. Be open to constructive criticism.