No sooner had I updated my ready-reckoner of bottle and can sizes to include nip bottles (275 ml) than all the cool kids started putting their beers in 440 ml cans – a weird size, which is fairly easy to compare to 330 but has very little else to commend it. I guess 440 ml cans are easier to get hold of than 500 – and you can sell a full one for pretty much the same price, which means three cans’ worth of beer in every 25 are pure profit. (I’ll give you a moment to check the arithmetic. That won’t be the last of it.)

Now, a ready-reckoner that included the pint, half-pint, third pint, 500 ml, 330 ml, 275 ml, the US pint, the US 12 oz **and** the 440 ml (and the nipperkin and the brown bowl) would be unwieldy to say the least; that’s a 9 by 9 table. Is there any way to simplify things, other than by just leaving stuff out?

Let me introduce you to the most important imperial measure you’ve never used: 1/72 of a pint. Also known as 7.891251 millilitres, which is to say (and this will be important later) very slightly more than seven and eight ninths (7.8888…). (How slightly? If you multiply out by 72 you get 568 exactly; a pint is actually 568.261 ml. So if you use the “seven and eight ninths” rule of thumb you’ll be off by two millilitres per gallon.)

Now, 1/72 of a pint is not a particularly useful measure in and of itself. What it **is** useful for is conversion. Without further ado, I give you:

**The Universal Ready Reckoner**

Third |
24 |

275 ml |
35 |

Half |
36 |

330 ml |
42 |

US 12 oz |
45 |

440 ml |
56 |

US pint |
60 |

500 ml |
63 |

Pint |
72 |

*First column: measure**Second column: how many 1/72s of a pint is this?*

These are all good to within 2 mls, apart from the 500 ml which is out by 3 (i.e. 63 * 7.888… = 497). Good enough for our purposes, which… well, what **are** our purposes? What’s this all about?

What this is all about is that, if you can memorise nine numbers and do a bit of arithmetic, you can convert the strengths of any measure of beer you’re ever likely to encounter back to the familiar pint (or back to any other measure you like). This in turn makes it possible to answer the eternal question *How many did I have last night**?*, even if what you had last night was 500 ml at 5%, 330 ml at 7% and 275 ml at 9%. Multiply the abv number by the size factor, add it all together and divide by 72, and you’ll have the equivalent strength of a single pint. It’s just a more elaborate equivalent of the calculation you might do if you were on halves all night (“*six halves at 6%, that’s like six pints at 3%, normally I’d be on 4%s, 18 over 4 is… four and a half pints*“).

In the example I gave above, you’ve got 500 ml (63/72) at 5%, 330 (42/72) at 7% and 275 (35/72) at 9%; so the calculation is ((63 * 5) + (42 * 7) + (35 * 9) / 72). Multiply out and sum the results, and you get 924/72, which reduces to 73/6; so it’s the equivalent of a pint at 12.2%, or slightly more than three pints at 4%. (In passing, it’s worth noting that 63 * 5 and 35 * 9 both come to the same number – 315 – which is to say that your 500 ml 5%er was exactly the same strength-wise as the 9% nip bottle (it’s actually 25 mils of alcohol vs 24.75).)

In practice it’s not as scary as it looks. The thing about 72 is that it’s 8 x 9 – the product of two cubed and three squared – giving it ten factors other than itself and 1; this makes the arithmetic a lot simpler than it might be. Some of those measures have got 5s in, admittedly, which does make life more difficult – it’s why the example above ends up with a prime number (73) – but you can generally get quite a long way by halving both sides and/or dividing by three.

No more numbers! Numbers finished! Hello again, reader who started skimming when all the numbers came in! That bit’s finished now, you can carry on reading!

Anyway… I realise this won’t be for everyone; when I said …*and do a bit of arithmetic* I wasn’t joking about the arithmetic. If you are comfortable messing about with numbers, though, I genuinely think this could be handy.

**Update 11th September **What should appear on the shelves at my friendly neighbourhood Tesco but a BrewDog/Evil Twin collab canned in a measure of… 402 ml. What fresh hell is this? Eyeballing the decimals tells me that it’s more or less 17/20ths of a US pint (although US pints don’t come in 20ths), or somewhere in hailing distance of 7/10 of an imperial pint, or… I give up. But it is 51/72 (or 17/24) of an imperial pint, give or take half a ml; if this measure is more widely adopted (as I sincerely hope it won’t be), I can at least find it a row in the table.

**Update to the Update** On closer inspection of the aforesaid can – and, indeed, on opening it – I realise that the beer is nitrogenated (a dispense method which lived up to its reputation by giving the beer a tight, creamy head). So presumably what they’ve done is take a plain old 440 ml can and subtract the space taken up by the widget. We can probably forget about the 17/24ths.