Julia EvansApr 13, 2023

today I'm thinking about the "don't use floating point for money" advice I hear all the time. It obviously has a lot of truth to it.

But -- Excel/Google Sheets uses floating point for all of its calculations, people use spreadsheets for money calculations all the time, and it generally seems to work just fine -- the results get rounded for display.

So I'm trying to figure out if there's a more nuanced guideline than "never use floating point for money".

Show threadRobApr 13, 2023

@b0rk My first reaction to this is kinda condescending, which is just “Don’t use excel or google sheets for money if you actually need accuracy” and I’m debating how much that’s genuine advice I’d stand behind.

Possibly losing pennies or dollars or thousands of dollars to rounding errors is gonna be small potatoes compared to other errors caused by the difficult-to-debug nature of spreadsheets (see for example https://www.science.org/content/article/one-five-genetics-papers-contains-errors-thanks-microsoft-excel).

One in five genetics papers contains errors thanks to Microsoft Excel

Show threadSam Tobin-HochstadtApr 13, 2023
@simrob @b0rk I think regardless of whether _you_ would stand behind that advice, in practice people who work with money professionally all use Excel all the time for it, including in complicated ways at large financial institutions.
Show threadRob
@samth …yes, obviously?
Apr 13, 2023 at 6:27pmWeb
Show threadSam Tobin-HochstadtApr 13, 2023
@simrob Right, and I think that situation calls for (a) humility from people who don't do that about whether maybe the people who do are actually more-expert at their area and (b) an answer to Julia's question as to why it works out.