Encounter difficulty calculator

Figuring out the difficulty of an encounter in tabletop RPGs can be difficult even with a difficulty table right next to you. Every group is different and not every player will want to play in a way that most efficiently uses their character's skills, which can make an encounter more difficult for the group as a whole.
With this encounter difficulty calculator you can fine tune everything to optimize the difficulty calculation for your specific group. It's based mostly on the D&D 5e system, but it's compatible with other Dungeons & Dragons systems and other RPG systems as well. The tool functions as follows:

Difficulty rating

As soon as you start changing anything in the input fields below, with the exception of the player and monster names/types, the tool will automatically update the difficulty rating. There's Easy, Medium, Hard, Deadly, and Potentially Impossible. These ratings are based on the thresholds you see in the table at the bottom of the page, which you can alter as you see fit.

The Potentially Impossible rating means you went beyond the Deadly rating, which could mean your party will face their doom should you use the encounter as is. Very capable players could potentially still handle it, but it obviously depends on how far you went beyond the Deadly threshold.

Warnings

I've added two types of warnings. The first is a warning for weaker characters. If a character is 5 or more levels below the strongest, a warning will display automatically. Depending on the game system you're using, this level difference could skew actual the difficulty of the encounter a lot as lower leveled characters might not be able to hit monsters deemed easy enough to beat by the higher leveled characters. Playing around with their modifier or thresholds could help with calculating the actual difficulty, but more on modifiers later.

The second warning is that of strong monsters. This warning triggers when a monster outclasses the lowest leveled player by far, increasing the risk of potentially one-shot killing this character. A risk not every party is willing to take.

Player & Monster customization

Below you'll find to separate tables with which you can add and customize players as you see fit. It could be as simple as X amount of Y level characters against X amount of Y leveled monsters, or you could customize every playing and every monster a little more using the extra modifier.
The modifier will multiply the score of the corresponding player(s)/monster(s), and is mostly intended to take into account wounded monsters, extra-capable players and similar difficulty affecting elements. For example, if you have two level 5 characters, but one of the players is highly optimized and knows exactly what they're doing, you could give that character a modifier of 1.5 or 2.0 as their skills make them that much better compared to the average player.

Default values

The default values are all listed and will be used if nothing is entered. So if the custom threshold checkbox isn't checked, the default values will be used. If no modifier is entered, 1.0 will be used, and so on.

Saving

There are 5 save & load sets, this way you can prepare a bunch of encounters in advance and load them during the actual game with ease. The saves are done locally in your browser, which means you can close your browser, open it back at a different time, and still load your saves just fine. Note that this only works for modern browsers and only if you're not using incognito mode. I advise to test it before you spend time writing out a lot of monsters.

Printing

It's also possible to simply print out the page to have it with you as a physical copy. Only the essential information will be printed. This can also be a good way to ensure you don't lose any large customizations you've made when browser data is deleted.