Calculation method
The tool enumerates every ordered dice outcome, making 1d6 exact 6 equal to 1/6 and 2d6 total 7 equal to 6/36. Use the distribution to set difficulty around the average.
Assumptions and limits
This is a tabletop design scenario using your inputs, not a prediction of player experience. Check your game???exact rules and edge cases before finalizing a design.
Related tools
Use an exact total distribution
Number of dice, faces per die, and target total define the result. The tool counts possible totals rather than assuming that every sum is equally likely; middle totals are usually more common than extremes.
Use the result in a design decision
For 2d6, a target of 7 is more common than 2 or 12. Test the complete target range when writing difficulty bands so adjacent labels do not conceal a dramatic probability jump.