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Most distances in 5e, especially in combat are multiples of 5 feet. Similar to to the person who asked How do you deal with non-metric based systems?, I live in Europe and US customary units are unfamiliar.

Contrary to some of the answers given to that question, I would like to simply treat 5 feet as 1 meter. This would mean that one square would be 1 meter by 1 meter, and that the base walking speed for Human characters would be 6 meters. Now 5 feet is actually slightly more than 1.5 meters, so this would mean that effectively squares get 50% narrower, walking speeds are 50% slower and units can get 50% closer to each other.

The advantages for me would be that my players and I would more easily be able to visualise distances and have to do less on-the-fly multiplication and division.

Are there any serious disadvantages to this? Especially considering I am going to be playing with people who have no experience with D&D or TTRPGs.

Anagkai
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Jasmijn
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    I'd consider 2 meters instead of 1 – Caleth Mar 22 '23 at 12:36
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    Yeah -- I seem to recall that in 4th Ed they actually specified that a grid square was either 5 feet or 2 meters, so while that's not technically 5e, I think it shows which way the devs like to go with it. – Darth Pseudonym Mar 22 '23 at 13:13
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    Thinking about three-foot squares reminded me of that conversation where in response to some people making fun of how big 5-foot squares are, the guy said, "Look, if the guy on my left has to do the turbo-macarena to charge up his Bolt of Flesh Melting and the guy on my right is doing every Bruce Lee move at the same time and the guy in front of me is flourishing a broadaxe like he's doing yoyo tricks with it, I'm going to give them enough elbow room not to get myself liquified, okay?" – Darth Pseudonym Mar 22 '23 at 13:20
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    I might try to put this toward an answer, but first: have you considered changing verbiage to "units"? 5 feet = 1 unit(s). – goodguy5 Mar 22 '23 at 14:58
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    For what it's worth, when GURPS put out GURPS Traveller, they took the Traveller deckplan square of 1.5m and called it 5 feet in their US distributions. – Jeff Zeitlin Mar 23 '23 at 12:36
  • This all could have been avoided, at the cost of slightly denser character arrangements, by doing everything in "paces". – Dave Mar 23 '23 at 21:08
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    The french translation of the core rulebooks for editions 3 and 3.5 used 1.5m as increment in place of the 5 feet one. It works pretty well. If we can consider the "official" rulebooks as some kind of reference, that seems to be the way it's intended to be equivalent. – Fractal Mar 23 '23 at 21:43
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    @Fractal That's also the standard for 5th edition. The conversion from ft to m is quite natural in this case, divide the length by 5, then add half. – Jupotter Mar 24 '23 at 06:55
  • As a very slight variant, you could use "yards". Yards are within 10% of the size of meters, but they sound old-fashioned. (A yard is 3 feet). This also means using 2 yards instead of 1 matches sizes closer (2 yards = 6 feet = 1.16x 5 feet). – Yakk Mar 24 '23 at 14:45
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    Just to clarify the comment by @JeffZeitlin - Traveller has used 1.5 m x 1.5 m squares in a game that uses only metric units ever since it was first released in 1977. (Two squares equal one "displacement ton" when working out starship deck plans.) Given that 1.5 m is only a centimetre or so off 5 feet, there is demonstrably no problem with running a metric/SI game using the same size grid squares. – KerrAvon2055 Mar 27 '23 at 06:26

3 Answers3

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Nothing changes as long as you scale everything proportionally

Assuming you convert every distance, range, size, speed, etc. using the conversion of 5 feet = 1 meter, the game mechanics will be essentially unchanged, except that you might have to deal with fractions a bit more often. The only problem you might run into is breaking verisimilitude. That is, you're effectively scaling every length down by one third. A walking speed of 1 m/s might feel unrealistically slow; a crossbow having an effective range of 6 meters might feel too short; in 3D space, treating a medium creature as being 1 meter tall (the height of a medium cube) might feel too short; and so on. Or this might all feel reasonable to you, in which case, go ahead and make the substitution.

Consider leveraging the grid rules to simplify the mechanics

If you feel like the above will be a problem for you or your players, consider this alternative: if you replace "meter" with "square", what you describe matches up closely with the "playing on a grid" variant rule. (Note: in this context, "square" as a measure of length/distance refers to the square's side length.) In light of this, perhaps you could adopt the grid-based rules for measuring lengths and then declare that, for the purposes of visualizing what's happening, a square is 1.5 meters on each side (or equivalently, 2 squares = 3 meters). Then you do all your math in whole numbers of squares instead of multiples of 1.5 meters, but you can still visualize things on the appropriate scale.

Ryan C. Thompson
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    AD&D 1e used "inches" for measuring ranges and movement rates; in a dungeon "1 inch" represents 10 feet, above ground "1 inch" represents 10 yards. (This goes back to the wargaming roots of the game -- literally measuring inches on the tabletop when using minatures). So there is a pretty long history of abstracting some distance measurements in that these "inches" correspond to an arbitrary, and in this case mutable, distance scale. – Dave Mar 22 '23 at 14:28
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    Narrative reasoning about non-combat situations can be affected, like how crowded it is to lie down for sleep with the max 10 creatures inside a Tiny Hut (10 ft radius = nearly two person-heights vs. 2 m being just over one person-height.) Unless like you say, you scale heights as well. Other than that, agreed, usually 3D space and creature heights vs. grid-square sizes don't tend to come up. Narrative intuition for speeds and distances (e.g. to jump a gap) could be a problem. – Peter Cordes Mar 23 '23 at 14:47
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No problems with balance...

If you are consistent, the balance doesn't change because AoEs become smaller and people and monsters are closer together and all effects retain the same relative ranges. No problem here.

...but it might be confusing

The rulebooks and other sources are still using feet for distances. You still have to do conversions. If you do the conversions on-the-fly this the math is only slightly easier and if you do them beforehand (for example note distances related to your class abilities), you might as well convert 5 feet to 1.5 m. I assume this problem will be especially relevant if your unexperienced players read official source material.

I typically just wing it

I have the same problem as you, I am also used to using SI units. What I typically do, is to say that 3 feet = 1 m. What is also helping is that I won't be too exact with distances. I just check if distances are roughly okay and when in doubt I rule in favor of the players. I don't see any benefit in being pedantic here but this depends on your play style. If you find exact distances important and like counting the squares, this style might not be for you.

Anagkai
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    +1 for your section on "it might be confusing" - mismatch from the rules is absolutely going to cause issues. – NotArch Mar 22 '23 at 13:38
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It would screw DnD realism even more than it already is.

Slight nitpick: you say that

effectively squares get 50% narrower, walking speeds are 50% slower

but 1/1.5 = 67%, so it's 33% (narrower/slower), not 50%.

Implications you might have missed

I don't think that you've considered all the implications:

Firstly, consider movement. A "standard" adventurer can move 12 squares, 60 ft in one turn (6 s game time) with a dash, which works out to 10 ft/s, 10.9 km/h, which for context is about half the speed that a top tier athlete can run a marathon. This feels right, considering the adventurer is in armor, with weapons, etc. A square of 1 m means a dash speed of 2 m/s, 7.2 km/h, which is coincidentally almost exactly the New York Walking Speed An adventurer using their 6 standard squares of movement without dashing, could get a ticket for walking too slowly in NY.

Secondly, consider weapons reach: 1 m is way too short with something like a longsword (average blade length of 0.9-1.1 m) held in a medium humanoid's arm, but 1.5 m is about right (I suspect this is what the 5 ft square was based off of).

Just use 1.5 m if you don't want to use Freedom Units, it's not too complicated.

Anagkai
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Eugene
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  • @terdon whoops, my dyslexia showing up, I misread it as less than. Changed it to an actual nitpick I just noticed, that it should be 33% not 50%. Re: Freedom Units, it's a common humorous name for Imperial, covered here: https://english.stackexchange.com/questions/378068/how-do-americans-refer-to-their-non-metric-system-in-everyday-circumstances. Will add a link in the answer. – Eugene Mar 23 '23 at 19:51
  • Oh wow. Thanks for that link, it helps put it in perspective. I thought you were indeed saying that with a straight face! – terdon Mar 23 '23 at 20:27