Encounter calculator?

[Mr Adventurer]

So I've knocked together a really basic spreadsheet to help me work out my encounters, totalling XP value and number of monsters so I can apply the # multiplier to work out the difficulty. But it's clunky as hell. Is there a better one somewhere? Preferably with a database of monster CRs integrated into it?

[MaxWilson]

Yes. Try http://kobold.club/enc

[Freelance GM]

Or try this one. (http://donjon.bin.sh/5e/calc/enc_size.html)

[Mr Adventurer]

Hey, both of these are really useful! Thanks!

[Kryx]

Top result on google is the one I commonly use:

http://dhmholley.co.uk/encounter-calculator-5th/

[Ninjadeadbeard]

Top result on google is the one I commonly use:

http://dhmholley.co.uk/encounter-calculator-5th/

This. I love this one, and it has served me well.

[Louro]

Using them.

5 member lv 8 party.
Add purple worm.
Over deadly encounter.

Another lv 8 member joins the party.
Over deadly turns into hard encounter.

Mmmm... They are all gonna die with this worm.
Good! DM aproves while evil laughing.

---
That 0.5 factor for parties over 5 members. Crazy.

[MaxWilson]

Using them.

5 member lv 8 party.
Add purple worm.
Over deadly encounter.

Another lv 8 member joins the party.
Over deadly turns into hard encounter.

Something's wrong with your math. There is never anything over Deadly (Deadly goes up to infinity), but if you have 6 level 8s against a single Purple Worm that is Medium, not Hard. What tool are you using to compute? It is wrong.

[Louro]

Yep, its medium. My bad.
I got quite surprised when such a dangerous beast went from 12.500 for a 5 members party to 5.400 for just one more member. I don't see such a diference in term of... of how many of them can survive, because I'm almost sure there will be casualties if they decide to face him. Well, it will be basically one death by turn. I might need to figure out how to give them an edge.

Using the Kobold club one, the best one IMO.

[MaxWilson]

Yep, its medium. My bad.
I got quite surprised when such a dangerous beast went from 12.500 for a 5 members party to 5.400 for just one more member. I don't see such a diference in term of... of how many of them can survive, because I'm almost sure there will be casualties if they decide to face him. Well, it will be basically one death by turn. I might need to figure out how to give them an edge.

Using the Kobold club one, the best one IMO.

You might be surprised how well the PCs do. 5E PCs are generally pretty hard to kill, and these guys are eighth level. It's more likely that the 5-man estimate ("Deadly") is overly pessimistic. Purple worms only have +9 to hit, so it's probably going to hit once per round for about 40 HP of damage per round on average, maybe swallowing somebody. Meanwhile, I don't know your party but I'd guesstimate you'll average about 15 points of damage per PC to it in return, so it should be dead in three rounds. Probably at least one PC will be knocked unconscious by then, but all it takes is a bonus action Healing Word to revive them. If the PCs tilt the odds in their favor with spells like Faerie Fire or even better Web/Evard's Black Tentacles, they'll do closer to 22 points of damage per turn (guesstimating) while taking only 25 or so points of damage per turn in return. In short, if you fight smart and Web it/use Cutting Words from a bard/etc., you'll do six times as much damage to it per turn as it does to you, and it will lose badly. Also, if the PCs know a purple worm is in the vicinity they have the chance to do things like cast Protection From Poison and Bless, which will make it even easier.

Remember that under Lanchester's Square Law, a party of six is more than twice as strong as a party of four. 50% more DPR/spells and 50% more HP makes a big difference.

The PCs might not be able to kill it before it gets away but they should almost certainly be able to force it to withdraw, unless of course you play it tricky and make the Purple Worm do things like burrow beneath somebody, pop up and swallow them, and burrow back down again in the same turn. If you play it that way it might be a TPK, especially if the Purple Worm takes a short rest to regain HP after eating a couple of PCs and then comes back for seconds and thirds.

[Louro]

Thanks for your comments.
So far I found out that encounter XP value is indeed below what it should be as you said. Setting hard and deadly situations they use to come out victorious with just some minor scratchs and one or two knocked members occasionally.

They are not aware of the worm. The BBEG (who they don't know yet) controlled it to reach the underneath cavern they are going in. Some NPCs are waiting for them and will use its poison (clue there). Some goblins will be casting thunder weave in the final room to call the worm... maybe I turn it into Dune (goblin worm raiders) or maybe they call for him and just run away.

I hadn't though about that bury and sneaky attack tactics... that would be nasty. The worm will be just pissed, will try to get a meal and get out if things get dangerous.

[Shining Wrath]

There's a lot of useful tools at this site (https://donjon.bin.sh/5e/calc/enc_size.html).