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Why Margins Are So Cool

Recently, I have found myself gravitating towards games that include a task resolution mechanic that includes a way to measure the margin of success on a check. It started over a year ago, with my short-lived Witchcraft campaign, and then flowed into my year-long Corporation game [1], and recently it became a requirement for picking the system [2] for my latest campaign, In Nomine. Of all the mechanical elements [3] of a game, this is by far, becoming one of my favorites. The best part is, that even if your game did not come with one, you can add one pretty easily.

Nuts and Bolts

Lets take a moment to look at the margin mechanic in a little detail. In many games a task check (skill, combat, etc) has a Boolean result of either Pass or Fail. Mechanics that utilize margins change that Boolean result into a spectrum of Pass and Fail. There are a few ways that the margin mechanic can be employed:

In addition the margin can be:

There are a few ways to determine the margin depending on the mechanics of the game system. Here are some of the most common:

As you can see the Margin mechanic is pretty flexible, but its real power comes when you pair the mechanic up with the GM…

Margins Are the GM’s Friend

It has been said countless times that the GM’s job is hard. It takes a lot to describe the action that is unfolding around your players, translating it into exciting prose that keeps your players interested and engaged. In the chaos of keeping all those elements together, we tend to take mental and verbal shortcuts in our narration. One of the most likely targets of these shortcuts are the descriptions of the outcomes of skill checks. Nothing is more painfully boring than saying something like, ” You jump across the chasm and land on the other side. Which direction do you go?”

You would like to vary your descriptions of such actions, but it is an easily forgotten task. That is where the margin comes into play. Because the Margin is baked into the mechanics, the GM has an instant reference of how well a player has accomplished a task. Now, that jump across the chasm has a few different possibilities:

In addition to aiding narration, there are a number of mechanical uses for the margin that can be used to help determine the outcomes of actions in a game.

One use is head-to-head contests.  In this case, two adversaries are engaged in an opposed challenge. Both make skill checks and record their margins. The margins are then compared and the winner is the one with the highest margin.
The margin of success can be used to give bonuses or penalties to other checks. A skill check that succeeded with a high enough margin, would create a bonus for a subsequent check.

For instance: A stealth check, to sneak up behind a guard, with a high margin of success, would create a bonus to strike the guard on the next turn.

Another mechanic is to use a margin as a way to measure extended checks. In this case several skill checks are required for a task, but rather than requiring a set number of successful checks, you instead require a fixed number of margin as the threshold for completing the task. This use, rewards checks that have succeeded by a high margin, because they will reach the total required in less skill checks.

For instance: A character is researching an ancient tome for a ritual. The GM decides that it will require a total margin of 20 to discover the ritual, and that each check requires 1 hour’s time. The player that rolls a high margin on one more rolls, will reach 20 faster than someone who is marginally successful each check.

Making Your Own Margin Mechanic

If your game has a margin mechanic in it, then you are already enjoying some of the benefits mentioned above, but what about games where there is not a margin mechanic? You are not shut out from this great mechanic. In many systems it is not hard to create a margin mechanic, as a house rule.

In any game that uses skill checks with target numbers (for instance: D&D 3.x and 4e) you can measure the difference between the roll and the target number.

For instance: Your Cleric is making a Diplomacy check in order to obtain a donation from a Baron, for his church. The DM sets the DC of the check at 15 (the Baron does not hand out money easily). The player rolls and gets a 30. With a 15 point margin, the DM decides that the Baron not only decides to donate, but makes a very generous donation.

In many cases, experienced DM’s may be doing such things already. If you are, that’s great, if you are not, consider it. In either case, you can extend the margin mechanic and use some of the mechanical aspects, discussed above, as well.

For instance: Your Rogue is locked in a room filling with poison gas. The gas does 1d6 damage per round. The DM decides that the trap has a DC of 20, and that it will require a total margin of 35 to disarm.

So Whats Your Margin?

The margin mechanic is a great tool for GM’s, giving them a narrative guide, as well as some fun mechanics for creating tension in their games. So are you playing a game that has a margin mechanic? Have you house ruled a margin mechanic into your game?  In what ways are you using margins?

14 Comments (Open | Close)

14 Comments To "Why Margins Are So Cool"

#1 Comment By AJSB On June 11, 2010 @ 4:33 am

The game I currently play in has a margin system, although it’s known as Degree of Success (WFRP 2nd ed). Our has been somewhat house-ruled so that on a successful check the tens digit (it’s a % based system, roll under skill to pass) gives degrees of success. it’s a quick and easy way to check (no maths involved) and allows higher skill characters to gain higher levels of success (as higher rolls can be passes).

In terms of mechanical effects, the DoS is used for everything you mentioned, and more! Descriptive flourishes (my character almost fell into a mass of thralls due to a very low success jump last week), bonuses, etc.

It’s also used for combat. The amount of damage done is your DoS+any applicable modifiers (e.g. weapon, strength etc). Reactive actions (dodge, parry, dispell) reduce the attacker’s DoS. A final DoS of less than 0 is a successful defence, otherwise your parry or dodge simply reduce the damage done. (You get your sword in the way, but not sufficently well to stop the blow. You get your head of the way, but the sword hits your shoulder instead.)

It’s a great system. I totally agree that everyone should do margin of success!

#2 Comment By mobuttu On June 11, 2010 @ 4:41 am

Heroquest2 is also a game based on that margins.

#3 Comment By MaW On June 11, 2010 @ 5:04 am

I play two games with such a mechanic.

The first is a straightforward difference mechanic, and it’s found in Paranoia. Being a very odd game, the players aren’t supposed to know about this kind of rule, but skill numbers range from 1 to 20, and you roll a d20 and aim to get below the skill number in order to succeed. The lower you get, the better the success is. Rolling a 20 usually causes something… else… to happen, and definitely comes under ‘exceptionally spectacular failure’. Especially with mutant powers, and anything involving nuclear weapons. Muahahaha.


The other game is Godlike. Godlike skill and combat checks are done using a pool of ten-sided dice (up to ten). Success is indicated by ‘matches’, which are multiple dice that come up with the same number. The margin comes from both how many dice are in the match, and what the number is. Quite often, the width – that is, the number of dice – is used to determine how fast it happened, while the number which comes up is used to determine how well you did the thing.

In combat, everyone rolls at the same time, and the widest goes first, possibly causing narrower rolls to fail due to being shot/hit/ripped to pieces by telekinesis/otherwise incapacitated. Tie breaks on ordering are done by number, so a match of tens beats a same-width match of fours.

Thus the GM has plenty of scope for degrees. Maybe you’re translating something written in German. You roll Brains+German, and get a match of two tens. Excellent! you produce a perfect translation, but it takes you a while. Maybe somebody else tried at the same time, and they got five sixes. They produce their translation much more quickly, but it’s sloppier and might not be so precisely accurate.

This is called the ‘one roll system’, because the one roll of up to 10d10 determines initiative, effect and damage in a combat round, without having to roll again (weapons are usually specced as things like ‘width in killing damage plus width in shock’, or ‘width plus two in shock’). Even hit location comes out of the roll – tens are a shot to the head, 5 or 6 the right arm, etc. My group’s getting on very well with it, although occasionally the GM will ask us to roll something else to figure out the subtleties.

We do definitely like degrees of success. Oh yes.

#4 Comment By Dunx On June 11, 2010 @ 7:30 am

I play in Savage Worlds which you’ve already noted is a good margin system (especially on the success end), but I run Call of Cthulhu with BRP. The base rules only really cover margins in combat (1/5 of skill to impale and do double damage, 96-00 – varying by weapon – to have your gun jam).

However, I usually run something closer to the original Rune Quest rules:

– roll under skill% to succeed
– roll under skill5 / 5 to get a Special
– roll under skill% / 20 to get a Critical
– roll over skill% to fail
– roll over 100 – ((100 – skill%) / 20) to get a Critical fail

I only have extreme failure at the outer limits, but sometimes the crit failures help the characters. One 1920s photographer was trying to take a picture of a baddie to distract him (he was on stage at the time) and utterly blew the roll – but the flash was magnesium powder (all that was available in 1920) so I ruled that the flash toppled over and set the baddie alight.

That was funny.

#5 Comment By Dunx On June 11, 2010 @ 7:31 am

s/skill5/skill%/, of course.

#6 Comment By Walt Ciechanowski On June 11, 2010 @ 7:46 am

Doctor Who: Adventures in Time and Space has a margin mechanic.

d20 games also have a margin mechanic, at least for combat. A critical hit is better than a regular hit.

Great article!

#7 Comment By DNAphil On June 11, 2010 @ 10:46 am

Sounds like I am not alone in my love for the Margin.

One of my favorite things to do with Margins are to make little mini-games with them. In Corporation, I used the margin mechanic to make a car chase that had threaded into the bad guys hacking this piece of technology. The chase was being handled by competing margin checks, and the hacking by a cumulative margin check. The outcome of the scene was in the hands of the players and the dice, it was a great way to run the scene. I had no idea how it was going to turn out.

#8 Comment By BryanB On June 11, 2010 @ 12:05 pm

I really like systems like Fate 3.0 where you can get additional benefits for rolling past what you need for success. Like getting the benefit of doing something faster or much better than what you needed or expected to do.

#9 Comment By Patrick Benson On June 11, 2010 @ 2:46 pm

As a huge fan of Fudge I love how margins can be used to add tension to a game. Barely succeeding can be just as dramatic as an amazing success, and an abysmal failure is a way to add cool to the game. Great article!

#10 Comment By Nojo On June 11, 2010 @ 3:36 pm

I <3 margins too!

Walt: I disagree that d20 crits are margins. If you only need to roll a 5 to succeed on a d20, and you roll a 15, that's a huge margin, but not a crit. If you need to roll a 19 and roll a 20, that's not much of a margin at all, but you get a crit.

AGSB: Dark Heresy and Rogue Trader also use Degree of Success. It's a lot of fun, and is based on WHFRP v2. I am stingier than your GM, and give one extra point of damage for every three degrees of success. I add that in at the end of all damage calculation. For weapons with a high rate of fire, I apply that only to the first shot.

#11 Comment By steamcrow On June 11, 2010 @ 5:10 pm

I once made an “Action Chart” for Runequest so that I could help quantify the level of success that different characters had for different actions.

It was really a pain until I discovered Fudge, which automatically lets you know your margin of success for opposed actions.

It’s one of the reasons that I dig fudge, and why I’m using it for my Monster Commute RPG.

It’s really cool to define things with a baseline for margins too.

This is a Good Chasm. (Requires a good to make it across cleanly. Fair is fine, but a Poor success is rather iffy.)

Great article.

#12 Comment By Scott Martin On June 11, 2010 @ 7:25 pm

I like margins quite a bit– most sessions I play use them. In our D&D game, the GM house ruled good margins on heal checks– normally it’s a DC 10 to give another player a chance to spend a healing surge and DC 15 to stabilize a fallen character. She granted a DC 25 heal check both effects– which was very cool, allowing strongly skilled characters to really shine and do more in a few seconds than most people.

#13 Comment By Walt Ciechanowski On June 11, 2010 @ 9:13 pm

@Nojo: I see your point, but the whole idea of margin mechanic is to grant something extra for a high roll. Most critical hit systems do this.

Technically, a d20 crit is a high margin of success; it just operates on a bell curve. You always have a 5% chance or less of having a great success when you roll.

#14 Comment By evil On June 12, 2010 @ 11:43 am

The only margin type rule I use right now is a Luck roll I’ve added to our D&D games. If the luck roll requires a 15 and you roll way above it, you get much luckier, if you roll a 5 you get really unlucky. After reading this article and seeing the feedback, though, my devious brain is working on all sorts of ways something like this could be included, maybe going so far as to just make up my own ruleset once more.