Dnd 5e Balancing Combat Encounters

 Rule #1 - Don't Try To Balance Encounters

Dungeons & Dragons 5th edition is a combat focused tabletop roleplaying game. A vast majority of player character abilities and spells focus on combat. There are the exceptions, but for the most part, it is a combat game by design. Unfortunately, this design is an oddity when it comes to how a DM is expected to manage combat encounters.

D&D 5e is built on the presumption that in an adventuring day, a party of PCs will participate in 6 encounters. Abilities and resources are balanced around this concept as is most of the combat mechanics. 2 encounters, short rest, 2 more, short rest, and the final 2 leading into a long rest. Or any combination of instances. 

With that in mind, if in your game the player characters only experience 1 or 2 encounters per short rest, combats are going to feel very much in favor of the players, who are essentially tackling each challenge at full strength instead of being whittled down over time. As a result, how you design and "balance" encounters will need to change.

Rule #2 - Make The Encounters Work For Your Game

The CR or challenge rating of a monster in 5e is a calculation of it's difficulty (within the aforementioned framework of the 6 encounter adventuring day). Bluntly, it's whack and I largely ignore it. What I do use it for is an estimate of monster power. As an example, an Ogre is challenge rating 2 meaning that a party of 4 player characters at level 2 will have a moderate challenge fighting that foe. It will feel easier when they are at full strength, and more difficult if they have fought a group of goblins earlier in the day. However, take CR with a grain of salt, because I once had 5 level 7 PCs completely destroy a CR 11 behir in only a couple of rounds. From that day forward I gave CR much less credence.

https://www.artstation.com/salamandrasan

Now as for your game. If your game finds PCs having multiple encounters per day, by all means utilize the CR system more readily, and also make use of encounter builders and encounter challenge calculators to your heart's content.

However, if you have maybe 2 or even 1 combats in an adventuring day, consider ramping up the difficulty of these encounters (in relation to the CR system) your PCs should be able to handle it (once they've hit about level 3, early levels are a whole other ball game). This is how I typically run my games, usually a couple of smaller fights with a climactic boss or mini-boss encounter that is a bit more cinematic or challenging.

In terms of how they fit into the challenge rating system, they were usually difficult or deadly encounters each time. The only issue with this approach is that you have to be careful not to totally destroy the PCs, so be aware of the monster's capabilities.

Rule #3 - You Are Allowed to Adapt, Be Ready

This claim may be controversial in some tabletop circles, but allow me to explain. When I was first learning the ins and outs of DMing combat, there were some instances where I needed to make a monster stronger or weaker because I misjudged the encounter I had randomly rolled or preconstructed. There were times when I gave an enemy a few more rounds of life, or a spell they may not necessarily have had access to because it made sense to me.

I think the main stipulation that has to be attached to any DM "cheating" is that it has to serve the story and the narrative, not the DMs ego. Yes, it can be frustrating to watch your finely crafted creature get creamed in a combat, but it is a learning experience. I do not condone stacking monster hit points when a monster should be alive because it's just strong, I do support it when sometimes for balance reasons, the standard monster stat block you're using is just too piddley for your high level players and they would otherwise get destroyed in one round.

Feel free to add more monsters as reinforcements, if it fits the narrative. Put the pressure on the PCs. But also have the bandits retreat when their leader has been struck by a lightning bolt from the sky or an arrow pierced their eye. Make choices that fit the story, and be ready and willing to adapt.

Rule #4 - Understand Action Economy

https://www.youtube.com/watch?v=1pxtrlJdxn0
(From Darkest Dungeon, but it still works)

In disregarding challenge rating, I have come to understand that action economy is the true deciding factor in determining how difficult a combat is.

The action economy denotes the value of how many action one side has over the other, usually the PCs over the monsters. 5 PCs and one boss, the PCs have 5 actions and you've maybe got one and a legendary action, that is heavily skewed in their favor. 

You could potentially throw a pack of 30 dire wolves at a high level party, and through their pack tactics and superior action economy, some hits would certainly get through and this encounter might be surprisingly challenging. They have more attack and actions than the PCs simple as that.

With my Behir example from before, I severely misjudged the power of action economy. The PCs could do so much  with only my Behir able to shoot a lightning beam and move, compared to even a single monk's flurry of blows, stunning strike etc. 

I "balance" encounters like this:

• Easy - Less monsters than PCs
• Medium - Monsters = to PCs
• Hard - +1 or +2 monsters to PCs
• Deadly - Boss monster + monsters = to PCs

Or something along those lines. I've really come to appreciate Pathfinder 2nd editions design philosophy, and how they handle crafting combats, but that is for a future article.

I hope my ramblings have put you somewhat at ease when it comes to "balancing" combat encounters. Ultimately, do what you think is best, and do what serves the story you are trying to tell WITH your players.