June 22, 2011

Containers, Capacity, and Units of Measure (made easy?)

This all started out innocently enough.

I wondered "How many flasks can be filled from a full barrel?".  I didn't like the container sizes in some of my various game books, so I started doing a few calculations of my own.  This quickly spiraled into creating a home-brewed system of measurements for my world of Ezzin.

I don't really know what compels me to do these things.  No doubt the alcohol helps.  Even so, I doubt many others would enjoy a couple days of researching and comparing Sumerian, Roman, Imperial, Metric and US systems of measurement.  I guess I'm one of the lucky ones.

In making this, I had two main goals.
  1. A slick, unified system that's easy to use. 
  2. A system that gives the impression of strange and antiquated units, difficult conversions, and odd fiddly bits.  For the sake of flavor and atmosphere mostly.
The metric system fulfills the first goal, but not the second.  So I set about making my own weird thing.  As a whole, I think it turned out pretty well.  However, I'm probably biased.

Weight/Volume of Coins
 On Ezzin, all coins weigh the same.  In truth it's to streamline gameplay, but I think I'll blame it on a powerful guild of merchants who've successfully standardized most systems of measure.

50 coins = 1 pound

A lot of containers will tear open from the weight before they are even half filled by any type of coin, so making the weight identical expedites most bookkeeping on the character sheets.  Still, there may be a "weightless bag" or some other craziness requiring me to know just how many coins can fit into a given container.  So I compared densities, crunched the numbers a little, and came up with this. 

Pp: is about the size of a dime.  30 per in3
Gp: is about the size of a penny.  25 per in3
Sp: is about the size of a quarter.  10 per in3
Cp: is about the size of a thick quarter.  8 per in3

These "amounts per cubic inch" are mainly just to give me some rough guidelines for my estimations.  There will always be gaps between the individual coins based on how they randomly fall and stack inside the container.  I won't feel bad about rounding here.

Measures of Volume 
That merchant guild I mentioned earlier has been especially keen to standardize the containers of every land.  This makes it easier to trade between realms and to divide or consolidate goods.  These units are used for both liquids and dry goods.  These are all approximations.  Individual containers might be a little larger or smaller than standard size.  Don't be shy about rounding up or down.

#of in3 --------------- Container/Name ------ Weight of Water

82944 ------------------ Butttun/Wagonload -------------- 512gal/3072 lb
55296 ----------------------- Tun/Cartload ----------------- 256gal/2048 lb
↑ x2
27648 ------------------------- Butt/Pipe -------------------- 128gal/1024 lb
↑ x2
13824 ------------------- Hogshead/Oxhead/Gur ------------ 64gal/512 lb
↑ x2
6912 ------------------- 4ft³/Barrel/Large Sack ------------- 32gal/256 lb
↑ x2
3456 ------------ Half-Barrel/Keg/Kilderkin/Sack ------- 16gal/128 lb
↑ x2
1728 -- 1ft³/Talent/Amphora/Bushel/Firkin/Small Sack --- 8gal/64 lb
↑ x2
864 --------------------- Urn//Bag/Saddle Bag ----------------- 4gal/32 lb
↑ x2
432 ------------------ Peck/Small Saddle Bag ---------------- 2gal/16 lb
↑ x2
216 -------------------------- Gallon/Jug ------------------------ 1gal/8 lb
↑ x2
108 ------------------------- Skin/Belt Pouch ------------------------- 4 lb
↑ x2
54 ------------- Liter/Bowl/Bottle/Quart/Small Pouch ----------- 2 lb
↑ x2
27 ------------------ Flask/Pint/Jar/Large Coin Purse ------------- 1 lb
↑ x2
13.5 ------------------------ Cup/Coin Purse --------------------------- 8oz
↑ x2
6.75 -------------------- Gill/Small Coin Purse ---------------------- 4oz
↑ x2
3.375 ----------------------- Egg/Jigger/Shot -------------------------- 2oz
↑ x2
1.6875 -------------------- Dose/Vial/Potion --------------------------- 1oz
↑ x2
0.84375 ------------------------ Spoon --------------------------------- 0.5oz
↑ x5
0.16875 --------------------- Button/Dram --------------------------- 0.1oz
↑ x50
0.003375 --------------------- Grain/Drop ------------------------- 0.002oz

Well, there it is.  Later, I'll come up with some dwarvish and elvish words for these units too.  Quite a few of those are real world units of measure, but little on that list matches exactly to real world sizes.  Those are all approximations, shaved or extended a bit until they line up neatly together.  If the players hound me about it, I'll blame the discrepancies on differences in gravity or something.  I doubt they'll ask. 

I've included some standard adventuring containers on the list.  These units represent standard sizes.  Individual sacks, flasks, wagons, or whatever might be a little larger or smaller.  Overall though, this makes for easy conversions when the characters move items from one container to another.  I can quickly see that a large sack full of dragon scales can be split up into 4 small sacks, or 8 saddle bags, or 4 saddle bags plus 2 small sacks.

You'll notice that the largest unit is equal to a Tun plus a Butt.  Called a Butttun... because I'm childish.  I also included a button as one of the smallest units, because I like to plan ahead.  I'm sure that a Butttun/Button miscommunication will be entertaining at some point.

The smallest unit is a grain of wheat.  These grains on Ezzin are a little smaller than the ones found on Earth.  Ezzin grains just so happen to be about the same size as a drop of water, which is rather convenient if you want to use the same units of measure for dry goods as you do for liquids.  Which I do.

So, what do you think?   Is this useful, or am I crazy?  I'd appreciate hearing some thoughts about what needs to be fixed, and what works well.


  1. I think this is useful and necessary: for my own games I have to know how much fits in that sack. But it pretty much never comes up in play, unless I'm messing with the players, in which case the merchant's guild deliberately uses awkward, annoying measures to force everyone to use their weights, and measures in town a are different from b next door, and...

    The one time I got the players to care was when all measures were based off the emperor's favourite concubine, so a finger of gin, a leg of wheat. And then someone had been delberately shrinking the concubine as part of a scam.

  2. Yeah, it's not something that comes up often. More often than not, I'll just make arbitrary decisions rather than consult my chart here. Still, the chart feels useful somehow, I dunno.

    I'll have to remember the shrinking concubine scam. I like that :-)

  3. looks like wizards has taken note:
    they have weights and measures for all manner of items (barrels they say holds 75 gallons)
    these conversion are nice when you want to know how many flasks you can fill after turning the water in this barrel into acid, or shinking this barrel of acid how much of a flask will it fill (about 15%, when it hits of course it goes back to being 75 gallons of acid or 600 flasks of acid at once. 600d6 with 600 splash....yeah..course i imagine most dms would say "no im not going to have them be hit with 75 gallons of acid at once, you get maybe 4-5 and a splash of 1 point over 600 feet")