The percent sign... just kidding. 10.4.3 broke the way precision is handled. In the View menu, set Precision to 4. 123456789 + 123 = 123500000 987654321 + 123 = 987700000 That's not how precision is supposed to work. The answers are totally wrong now. Even worse, try setting the precision to 3. 123456789 + 123 = 1 987654321 + 123 = 9 Um, what? Someone also mentioned this at Apple Discussions: Set the precision to 4. 123456789 + 234567891 = 3 Based on that example, I was able to figure out more examples: Set the precision to 8. 12345678 + 99654322 = 1 999999999 - 1 = 1000000000 Yeah, the calculator is broken. This is what I mean. There's bugs and glitches everywhere, yet NOBODY REALIZES IT. Another thread had comments such as these: This is exactly the kind of attitude that bothers me. People act like problems don't exist because they don't notice any problems. People also have too much faith in software. No wonder they don't notice any problems. They assume software is doing everything correctly. Even worse, from searching Google, it seems the calculator has had a spotty history. It seems Apple has always had trouble making a calculator that works properly. I'm getting fed up with Macs. I can't even trust the results of a simple calculator. I have other gripes with the calculator as well. Set the precision to 16. 62 + 40% = 62.3999999999999986 62 * .4 = 24.8000000000000007 Before someone lectures me on floating-point arithmetic and rounding errors, I understand the problem. That doesn't change the fact that the answer is wrong, and that doesn't mean it's not possible to make a calculator without this problem. In fact, the calculator in Windows has greater precision without this problem. Also, why isn't it possible to open more than one calculator window? That's a stupid limitation. I also hate how I have to wait for the silly button press animations to finish before the numbers show up. If you don't think that's annoying, try pressing a bunch of numbers really fast. This is the crappiest calculator program I've ever used.