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.

📉 Falling 0.4x Science
2,948
Comments
19
Years Active
5
Top Authors
#1814
Topic ID

Activity Over Time

2008
7
2009
24
2010
40
2011
50
2012
81
2013
96
2014
95
2015
128
2016
138
2017
147
2018
160
2019
178
2020
158
2021
280
2022
360
2023
355
2024
340
2025
281
2026
30

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.