10K, Ten K, or just 6.2 Damned Miles?

I don’t think I’ve ever seen it as “ten K”?

But for the right voice, “6.2 Damned Miles” works too.

They're called 10k when publicized as races. I think it's one of those abbreviations that has entered our popular, and maybe official, lexicon.

What the main character calls them is another matter, of course. I don't know anyone who describes road races in terms of miles anymore, but if your main character finds the metric system irritating, or has another reason to put it that way, then why not if it's written in his voice?

If I'm going to use K instead of kilometers, I use 10: 10K. It will look fine to your readers. But I also use ten klicks if I want to spell it out and I'm not referring to a race name.

Harder for me since I'm not in a metric zone is what to call half a meter. In US English that would be a couple feet or a foot and a half. Dividing meters up and using centimeters instead of inches is really awkward in my brain. But it's sci-fi, in the future in a human colony in another star system. There's no way they wouldn't have adopted metric.

Hi Maryn,

Due to common use, I'd vote 10K. CMOS doesn't have guidance on this specific issue (as I found to my chagrin a year or two ago when I tried to look it up). The closest thing I found was CMOS 9.16, which covers numbers with distances such as "50 km (kilometers); a 50 km race," but that doesn't quite apply to what you're asking, since in most contexts, race distances are referred to with K (or k), not km. Still, that guideline is enough to land me solidly on the numbers side of things. From there, I'd apply the general guideline of following the more common presentation; in this case, 10K versus 10k.

CMOS's general rule is to write out numbers in dialogue, but there's that whole "This practice requires editorial discretion" bit, and given their examples of when to opt for numerals, I'd go with 10K in dialogue as well.

However, seeing 10K at the beginning of a sentence would make my inner editor cringe (at least in most contexts). Is it possible to reword those instances so that you don't have to start a sentence with a number? If not, I think I'd recommend sticking with 10K there (much like military time remains in numerals even if it starts a sentence). But rephrasing would be my preferred option.

CMoS 16th offers two entries:

For non-technical: "Some students live fifteen kilometers from the school" (9.13)
For technical: "50 km, a 50 km race" (9.16)

But 50K is fine for colloquials and fiction. (I always think of the army term when I see it: 50 klicks)

CMoS also does say that the likes of dates etc that start a sentence should ideally be wrtten out, so fifty kilometers...

I don't automatically think of kilometers if someone says "10k" because k just means a thousand. For example, "he earns 30k" - obviously that's money. You could have 10k feet if you want, it's not just for metric. The long form of 10k is not 10 kilometers, it's 10,000. The short form of 10 kilometers is 10km. Runners saying "I ran a 5k" or "I ran a 10k" the long form would be 5,000m and 10,000m which means the same as 5km and 10km because that's how metric works, but the races are referred to by their distances in metres, not km. https://www.bbc.co.uk/sport/av/athletics/47186747



Kilometers is abbreviated to km (must be lower case). K is Kelvin, which is a unit of temperature. 10K is incredibly cold - so cold the air would be solid. Abbreviating kilometers as K is incorrect and potentially confusing.

10k meaning 10,000 would have to be 10k with a lower case k because the prefix used when you have 1,000 of any particular unit is a lower case k, e.g. km = kilometers, kW = kilowatts, etc. But I don't think there's an actual convention for using k to mean 1,000 as in the number, as it's informal language. However capital K just looks wrong and makes me think of Kelvin.

https://i.pinimg.com/originals/80/50/25/8050255105358e0fd4b33654bfb9cb26.jpg