Some of the most enjoyable and exciting parts of roleplaying come when the players take actions that aren’t quite covered by the rulebook. However, this often leaves DMs having to ponder seemingly bizarre questions – such as how much damage someone takes when a brontosaurus drops on on their head.

As well as coming up with names, NPCs and plot hooks on the fly, improvising damage values is an important skill that DMs need to develop. As with so many other aspects of DMing this is both an art and a science, with a need to balance out what makes sense by the rules with what fits in with the current scene.

For example, how much damage should a creature take if they fall in a lava pit? Logic dictates that it should really be a straight-up instant kill, but player characters be scorched with gouts of draconic flame or fall foul of deadly poison and be right as rain after a decant nap, so that doesn’t feel right either.

Fortunately, there are a few tools we can use to make this task a little easier.

The Commoner Question

One of the easiest ways to give you a starting point is to consider how badly the damage would hurt a commoner.

In 5E a generic commoner can take four points of damage before they go down, while eight is enough to kill them stone dead. This means that a d8 worth of damage – such as a decent hit from a longsword – is likely to leave them bleeding on the floor and has a chance to kill them outright, which all feels fairly appropriate.

We can apply this same thinking to something like being tossed through a tavern window during a bar brawl. There’s a chance that a random peasant may get badly injured after an attack like this and potentially even die without some medical assistance, but it doesn’t really feel like it should instantly kill them. This means that it should do something like a d4 or a d6 of damage, depending on how vicious the toss is.

On the other side of the coin it’s obvious that something like having a building collapse around them should kill a commoner more often than not. Therefore the damage should average out somewhere around eight, which means 2d8 or possibly even 2d10 if you want to make it more dangerous.

If needed, this principle can be scaled up somewhat by considering what kind of force is needed to take down a bear or an ogre – a single shot from a short bow shouldn’t be anywhere near enough to bring them down, for example, but a direct hit with a ballista should have a good chance of pinning them to the nearest wall.

However, this doesn’t work for magical or incredibly unnatural creatures, or for humanoids that have special abilities or skills such as elite fighters or magic users who tend to have their damage abstracted into ‘getting tired’ or ‘running out of luck’.

The technique also only really works at all for comparatively mundane sources of damage. Most DMs can at least imagine the kind of damage a crossbow bolt could do, but would find it hard to know how badly they would fare if a malevolent demon entity ripped out their soul, for example.

Even then it breaks down as the numbers begins to climb. Clearly a mountain falling on someone should deal more damage than a mere farmhouse, but how much more?

Compare and Contrast

Fortunately, while the rules may not cover every kind of situation out there, between the spells and weaponry on offer it does provide examples for an awful lot of weird and wonderful threats.

Exploding flour mill? That feels like it should be in the same ballpark as a Fireball.

Smashed by a marble pillar? I guess that would feel something like being whacked by a heavy maul.

Thoughts assailed with images of horror and existential dread? Seems like something a Mindflayer would do with its mindblast power.

Being able to conjure up the stats for all these abilities and spells at will is tricky and takes substantial experience, but you only need a few numbers in your head to get a start. The archetypal level three ‘blow up/blast this patch of land’ spells deal 8d6, while the biggest mundane weapons deal 1d12.

A good comparison for situations where creatures are thrown into walls or slammed into the ground is to think how far they would have had to fall to achieve the same effect. The rules state that for every 10 ft. the damage increases by 1d6, so if you’d guess that being punted across the room by a giant should hurn as much as falling from a fifth-floor window it should deal around 5d6 damage.

Feel the Burn

Sometimes, however, using these kind of rules doesn’t feel quite right. Many DMs – myself included – like to reward players for doing cool or interesting things in combat, and also give the monsters a chance to do something both unexpected and highly effective.

Even if the players are at higher levels it should still feel cool when they choose to kick the villain into the fireplace rather than just take another hack with their broadsword. However, if we’re being honest that trip into the flames shouldn’t really do all that damage – maybe 1d6 when they enter and another 1d6 when they start their turn there. This averages out at just seven damage, which is pretty lame when compared to the 11 or 12 average they would cause with an enchanted longsword wielded in both hands.

With this in mind, there’s nothing all that wrong with maybe boosting the damage a little bit so it’s at least in line with other abilities being used at that level.

This kind of scaling up should probably work both ways, for the sake of consistency if nothing else, but beware of giving too much ‘free’ damage to your creatures. If your players are regular DMs or simply very rules-savvy they probably have a good idea of how deadly certain hazards should be, and may get a little grumpy if they feel like you’re ramping up the danger of a situation arbitrarily.

Inevitably you’ll make some mistakes that you’ll only notice hours later while tidying up the table, but that’s fine. As with most other improvisation skills the more you come up with damage rolls the more natural it will feel.