According to the World Health Organization, approximately 1.35 million people die each year due to road traffic crashes. In the United States, 31% of all traffic-related deaths involve alcohol. In Canada, that figure is 34%. In Australia, it's 30%. And in the United Kingdom, it's 16%.
Sure, these countries are on the high end of the spectrum, with most other countries falling somewhere between 15% and 20%. However, even if we take an extremely conservative estimate and say that, globally, only 10% of all traffic-related deaths involve alcohol, that's still over 100,000 preventable deaths every year.
Most people don't drink and drive. Since 1997, the Victorian Police in Australia have breath tested more than 24 million drivers, and they found that 99.7% of all drivers recorded blood alcohol levels below the legal limit. The main reason given for drink-driving? They didn't think they were over the limit.
So it's pretty clear that most people actively try to do the right thing by not drinking and driving. And of the few people who do end up drink-driving, most of them think that they're under the legal limit and that they're not too drunk to drive.
That's why a BAC calculator is so important: If you're a good person who doesn't plan on drinking and driving, an estimate from a BAC calculator might be enough to dissuade you from driving. If you're ever unsure, pick the safe option and find another way home.