The Spell Effectiveness Calculator
I'd like to present you with my newest project, a very small application that will help you figure out the chance your spell has to succeed versus the average abilities of the chosen challenge rating. To run it, make sure you have the most recent Java Runtive Environment version.

The GUI (stands for graphical user interface) is really straightforward - you enter the DC of your spell, your caster level and the CR you're testing your spell against; tick the appropriate boxes for your spell (e.g. if you're testing Ray of Enfeeblement you'll only tick the 'SR' box, while against Phantasmal Killer you'll have to tick 'Fort', 'Will' and 'SR'. Finally, press calculate and the bars under the button should be populated with the statistical chances your spell has to succeed - if a saving throw or spell resistance is not ticked, the appropriate bars will have a 'not applicable' indication on them.

Important: Make sure that you close the application using File->Exit or the Ctrl+Q shortcut and not the "X" button.

The average abilities are taken from an old graph I once made for the old Wizards' Handbook, back on 339, using Cubeknight's critter filter:

Download Link

If you have any problems, suggestions or you want me to implement more features (I plan to add attack rolls, too, totally forgot about them!), just leave me a comment. 
Posted by
On Monday, January 4, 2016 at 7:35 AM


  1. (Tempest here. Dunno why it isn't identifying me properly.)

    Um, wow. For some reason my feed subscription to your blog didn't detect you'd posted anything, so I check manually and am treated to this gem. Sadly, I'm on a work computer and can't check it here, but will investigate at the first opportunity. Thank you for all your hard work!

    (I'd been writing similar tools in various spreadsheet programs for assorted expected damage calculations, based on what I could recover from discussions on CritterFilter, but never got around to doing a good one for spells.)

    Out of curiosity, did you just use the numbers from the graph, or did you manage to preserve CritterFilter? I'd almost give my left arm to have that database again.

  2. Hey Tempest! Good to hear from you :D

    If you've got those spreadsheets available, we can easily make them in applications like this one, so try to dig 'em up!

    I used the numbers from the graph, which where actually derived from the Critter Filter average numbers. Some CRs have a very small amount of creatures, so that's why there are some weird results (for instance, CR with 16 SR), but the graph is mostly acurate.

    However get ready to lose your arm :P Some months ago I contacted Cubeknight by email and he managed to dig up the .sql file that created the database! Now it's in .sql format, so it's kinda difficult to create a standalone application to upload it on a blog/website and distribute it, but I may cook up something (by the way suggestions on what to do are welcome!).

    Hope you solve that subscription issue - or I might have broken something - if it's not fixed, let me know!

  3. (Still no clue why it isn't identifying me, but this is Tempest.)

    The spreadsheets I've got are mostly in Google Docs (our group tends to use that to coordinate between sessions or share builds), and the tools tend to be either too generic (i.e. "fill out a basic character sheet given a few simple parameters, such as number of levels and a class skeleton" or too specific (i.e. "given an ECL, and an attack bonus with a weapon, read the touch ACs of monsters within 4 CRs of that ECL and determine expected bonus damage from the Avalanche of Blades + Combat Rhythm trick" - I eventually built a version of that for a purely experimental build (designed to taunt AoO tanks) that used unarmed strikes _without_ Improved Unarmed Strike during that stunt, which leads to an interesting interaction with Robilar's Gambit if the enemy is stupid enough to act on your provocations). Thus, I don't think most of them would be worth sharing.

    The only one that would be of general use to people is still in development - a spreadsheet that is intended as a complete campaign manager, tracking builds, generating character sheets, a tactical overview of the whole party, managing loot discovered/sold/allocated (currently assuming a single party bank account rather than Gygaxian-style individual divvies, but I have an alpha for that system too), handling item creation (with or without artificer tricks; this also functions as a wishlist and as a crafting scheduler), and so on, with assorted attempts to provide feedback on loot:XP ratios for DMs (i.e. substituting XP for level and regressing WBL onto XP, then reading current XP and comparing it to the sum of the character's gear and share of the loot). This is basically just a consolidation of all my general-purpose tools written in a way that lets them talk to each other; if you're interested, mail me (you should be able to get my mail from the blog admin tools), and I'll share what I've got with you.

    As for CritterFilter, I'll miss the left arm, but GO CUBE! I'm not sure a truly standalone app would be needed - the original was just a PHP site reading that database, and that was really popular in its own right. (I'm not quite sure how to go about making it offline either, to be honest - it's hilariously bad form, but a cheap shortcut would be to write an encapsulated site that reads the database using JavaScript or Ajax, specifying a relative path for the database itself, and then just releasing it as a downloadable *website* rather than a true EXE.)

    And finally, as for the subscription, I've added the RSS feed again and it still didn't work - the RSS only goes up to the divine crusader. Either the software's set up for a manual RSS update (no idea if Blogspot can do that, but...) or it's just not automatically updating for some other reason.