How much data does iMessage use?

I have 300MB of data per month. Inreally don't want to go over. I send between 3000-5000 texts a month, not all to people with iPhones. How many iMessage texts could I potentially send on my plan?

1 imessage can range from 1KB to 1MB, depending on if its just a message or if your attaching pics to it… It is impossible to answer this question without knowing your usage pattern on imessages