I know, I know. You've heard Google cry "Algorithm change!" before, and it seemed like nothing happened. But this time it's different.

Unlike the last few updates, Google has said their newest algorithm change is going to be one of the biggest to date. Starting April 21, Google is going to penalize any websites that aren't optimized for mobile devices.

If your site is already optimized for mobile, you're golden. Keep doing what you're doing. If not, you've got some work to do. Luckily, you've got a couple of weeks to make it happen.

Creating a responsive design on your website ensures it'll look perfect on any device. To do this, use sites like WordPress, SquareSpace or GoDaddy. Otherwise, you can hire a programmer or a company to convert your website.

Investing in creating a stellar mobile website is worth it — even if you're a brick-and-mortar retail store.

Read on to discover three reasons why a mobile website is a necessity for your business.

1. If you're not optimized for mobile, you're losing money

There are more than 1.5 billion people surfing the Web on a mobile device. Of those, 63 percent expect they'll be doing more mobile shopping over the next couple of years.

And mobile shoppers are already spending a lot of money. In 2014, people were expected to spend over $114 billion online, according to Forrester Research.

If your site isn't optimized for mobile, you can bid those customers farewell. A whopping 30 percent of mobile shoppers abandon purchases if the cart isn't optimized for their device. Ouch.

2. Mobile matters to your customers

Global mobile traffic accounts for 15 percent of all Web traffic — and that number is growing rapidly.

Mobile users may have the shortest attention span of any Web user. They're on the go, so they want their information fast. If your website takes longer than three seconds to load, 57 percent of your mobile users will leave your website and go to a competitor.

Three seconds seems like it passes in the blink of an eye, but on a smartphone it feels like an eternity. Open up your website right now on your phone, and see how long it takes to load. If it's longer than three seconds, you've got to speed up the loading time.

3. On mobile, you get better conversions

Getting users to convert on your desktop site can feel like you're rolling a boulder up a steep hill. Yes, they are converting, but slowly.

Mobile shoppers are the total opposite. Shoppers and browsers on mobile make quick, snappy decisions. 88 percent of people admit that shopping on a mobile device makes them make more spontaneous purchases — that is, if your website is to their liking.

In fact, shoppers on mobile-optimized sites convert 160 percent times more than shoppers on nonoptimized sites. That should be incentive enough to adjust your website.