Update 2016-09-17: Fixed presets (src).
Update 2011-04-27: Removed the "free" presets; fixed "success1.php" so it links back to the correct page.
Update 2011-03-17: upgrading from +10 to +11 with HD is now completely "safe" so check the "no risk" box if that is what you are calculating.
These flexible calculators allow you to test a wide range of hypothetical scenarios, including those not possible in the game.
You're going to upgrade that armor to +11, and you won't stop until you make it.
Question 1: How much would you spend, on average?
This time you have one piece of equipment and an unlimited amount of other virtual resources (zeny, elunium, etc.) ... and also you refuse to spend more than X kafra points.
Question 2: What are your chances of getting the upgrade you want?
Intuitively: If an "infinite" number of people tried for the same upgrade using at most X kafra points, what percent of them succeeded?
Here's the older version that also assumes unlimited gear. It's not as useful now that it's no longer possible to upgrade safely with HD ores.