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Interesting how Microsoft and Google have different ideas of how percentage key (%) should work.

Relevant post by Raymond Chen:

“How does the [Windows] calculator percent key work?”

http://blogs.msdn.com/b/oldnewthing/archive/2008/01/10/70474...

Implementing % button, Google chose an approach which is more mathematically sensible but arguably less obvious to users. For Google, 10% just an alias for 0.1. This means that if you want to calculate how much a dress with a price of $299 costs with a 20% discount, type in

  299 + 299 × 20%

Perhaps, this is exactly how you think % should work.

Microsoft, however, chose to make “%” key more user-friendly, perhaps sacrificing some consistency. Windows calculator tries to use the last computed value as “the whole”. Therefore,

  299 - 20%

will give you how much a $299 dress costs with 20% discount, and

  299 + 5% - 20%

will help you calculate 5% tax before applying the discount.

Sadly, Google thinks

  500 + 1% = 500.01

which is really not that helpful.

3 comments

I don't get it, if i try 500 + 1% on Google i get 505 http://sadpanda.us/images/1112074-RA9OURZ.png

You get a different result if you click the buttons versus performing a google search.

which I think it is exactly how I would expect it to work: If I ask a question, I expect the system to guess what I really want to know and give me an answer.

But a calculator should work like a calculator.

Still a pretty big inconsistency.

500 + 1% typed right in calculator displays "500 + 1% = 500.01" in the calculator.

500 + 1% typed in the search box displays "500 + 1% = 505" in the calculator too.

It's probably due to the search result being returned by some server at Google while the other one is computed locally through some client-side JS logic. I think they'll notice and unify the behavior at some point.

"But a calculator should work like a calculator."

Yes, and no physical calculator I have ever seen would give 500.01 for "500 + 1%".

I just tested it and the percent key in the Google calculator doesn't work like the one described in the linked article. It really just divides by 100.

3 + 5% = 3 + 0.05 = 3.05

Sorry, I just reworded my comment to make it more clear.

This article is about Windows calculator and I'm comparing two different approaches.

Google went with simple 10% = 0.1 here, like you say.

The way Microsoft did it is the same way most physical calculators I've seen work.