Someone asked about probabilities of opposed rolls in Runequest: roleplaying in Glorantha, and was kind enough to explain the dicing mechanics for me. Here is a spreadhsheet that calculates those probabilities: https://docs.google.com/spreadsheets/d/1fZxVVryVpszUtibyZm3VEIIeVowkX8M6fdmjVJMDEDg/edit?usp=sharing
Feel free to explore, make copies and so on. If there are any problems, please let me know. Most of the workings should be pretty obvious and I did not use any advanced spreadsheet magic. The sheet for probabilities in case of draws does contain one ugly formula, because it was easier to calculate it and write it as a formula than it was to figure out whether Google sheets manages sum notation (the one with capital sigma that sums over indices).
Given the size of the document, there is bound to be a bug or two lurking somewhere. Trust the results at your own responsibility.
I am led to expect a post at Adept play that compares these probabilities with the resistance table. Another interesting comparison would be between this method and the humble d100 plus skill.