Generally, when the topic of math prerequisites for computer careers comes up, people talk about calculus. Calculus is a requirement or recommendation for most undergraduate computer science degrees I know of, and usually recommended to high school students interested in making a career of computers as well. I took calculus myself, but I've never actually found it very useful for my career in computing and I know many excellent programmers, system administrators and database administrators who have not in fact taken calculus, nor ever missed it. My friends who are engineers involved in things like chip design and fabrication have, in fact, needed calculus, but that is not a general rule. (And in fact, their degrees are in things like materials engineering, which can be but is not necessarily a computer field.) After 15 years in IT, what I've found that I really needed math wise was statistics.

Understanding statistics is crucial to be effective as an IT professional in so many ways. Lord Kelvin said "To measure is to know." and "If you can not measure it, you can not improve it." (A more modern version is "What you measure is what you achieve.") Statistics helps you know what to measure. Statistics is the tool lets you know whether one option is really significantly better than another. It helps you share information in a way that truly allows you to influence decisions - being able to say "In our testing, we found that this product allowed us to complete tasks 15% faster than the product we are using now," is much more effective in swaying decision makers than "We (the programmers) like this one better."

If you are producing web content, is it more effective for you to produce more content or tweak your layout or focus on search engine optimization? Statistics is the tool set you need to determine which is the most effective and which effects are likely just random or due to other factors like a general upward trend in hits to your site over time.

If you think using a tool or particular approach would make you more effective at your job, statistics are the way to prove to your boss that it makes you effective enough to pay for the tool or otherwise make the choice you want effective. (Or conversely, it could show you that it's not worth asking for.)

If you need to estimate how long it will take you to finish a project, you can guess or you can use statistics to estimate based on past projects. Over time, the late will give you better results. Better estimates mean more stress for you and a happier boss or client, which can only lead to better opportunities for you. Statistics is also the tool that can allow you to find the truth in sales speak to determine whether a product is sufficiently better than what you are currently using to make the pain of changing worth it.

So, my advice, focus on statistics and don't worry about calculus unless and until you specialize in an area where it's needed.