SI Prefix Usage Debate

Comments discuss inconsistencies in using SI prefixes like mega- (Mg for megagram/tonne) versus common notations such as k kg or tonne, and parallels to financial abbreviations like K for thousand and M/MM for million.

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#1814
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Keywords

US EJ OP SI NIST UK www.nist force.cfm MM BTU km grams unit si 1000 mm units billion calories 10

Sample Comments

fegu • Oct 10, 2016 • View on HN

(Why is 1000 a k for kilo, but a million is MM, not M for mega?)

Ziomislaw • May 25, 2012 • View on HN

Just use kk (kilo*kilo) for million :) everybody is happy?

gumby • Aug 8, 2021 • View on HN

What's wrong with saying "tonne" instead of "billion grams"

Chris2048 • May 2, 2024 • View on HN

perhaps we should use kilo-millions?

adgjlsfhk1 • Mar 2, 2023 • View on HN

that's why the correct unit here would be megakilograms :)

geraldhh • Aug 6, 2023 • View on HN

please stop using "MM" it's not in line with decimal prefixes and unnecessarily confusing

pmontra • Jul 6, 2021 • View on HN

Same reason for we say 1000 km instead of 1 Mm, or Sun to Earth 150 M km instead of 150 Gm. Some units are usual in some contexts, some are not. In one word, habits.

ImPostingOnHN • Dec 6, 2025 • View on HN

America largely uses K,M,BEither OP is incorrect, or not American

bombcar • Dec 3, 2022 • View on HN

We need more uses of long and short - a kilometer is a short mile, a kilogram is a long pound, etc.

p1mrx • Sep 8, 2021 • View on HN

Tera/giga are globally standardized; trillion/billion are ambiguous.