Strength training is essential to developing and maintaining the ability to perform both daily functional activities (like lifting a bag of groceries or a child) and recreational activities you enjoy. One of the best ways to build strength is by lifting some form of weight, and the barbell has become the standardized weight implement used in competitions: the Olympics and powerlifting.
If you are considering adding a barbell to your home fitness collection, there are two main options: the standard bar and the Olympic bar. Overall, the main distinction between the two comes down to size: the standard bar is smaller in various ways.
The standard bar is shorter: an Olympic bar is about 7 feet long (2.2 meters) while a standard bar is usually 5 to 6 feet. (Note that "standard" is a misnomer since there are no competition standards that apply to this type of bar.) The standard bar is also lighter: an Olympic bar weighs 45 pounds while a standard bar usually weighs around 20 pounds. The longer bar can be used with wider racks that are more stable, especially when adding or removing plates.
The bars also differ in diameter. First, there's the diameter of the inner section of the bar between the plates where you grip it. The Olympic bar is about 1.1 inches (28 millimeters) while the standard bar is usually around 1.0625 inches (27 millimeters). Due to the difference in bar lengths, the length of the grip area is also shorter on standard bars.
The bar ends have a more significant difference in diameter. The standard bar stays the same (around 1 inch) while the Olympic bar gets much larger: about 2 inches (50 millimeters). Thus, each bar uses different plates: the standard bar uses plates with holes around 1 inch while the Olympic bar plates have holes around 2 inches.
While Olympic plates can come in various heights depending on the weight, the standardized height for competition is about 18 inches (450 millimeters). This is the height of a 45-pound plate. However, lighter plates can also be of this same height by using "bumper plates." These are coated in solid rubber to allow the bar to be dropped from considerable height, as happens during Olympic lifts (the snatch and the clean-and-jerk). Bumper plates also allow you to raise the bar off the floor the same height as a 45-pound plate but with a smaller load which is helpful for people who aren't yet strong enough to deadlift a 135-pound load (two 45-pound plates plus the 45-pound bar). But this comes at a price: bumper plates are much more expensive than the usual cast iron.
To get a standard bar up to the usual deadlifting height requires putting it on a rack or platforms because the plates are smaller. Since deadlifting is one of the best things you can do with a barbell, that's a real consideration.
One other notable difference in the bars is that Olympic bars have rotating sleeves. This means the bar ends where the plates are loaded spin independently of the inside bar where you grip it. This is important when doing lifts that require rotating the bar quickly as the Olympic lifts do. You don't want to be trying to quickly spin the plates too! This is not important for people who don't spin the bar (for most folks, that means doing cleans--moving the bar from below your waist up to the "racked" position at your shoulders) but if you ever do you'll definitely want this feature.
So if you're planning to get a barbell for home use, here are some considerations to help you select the best bar for you:
Generally, I recommend an Olympic bar if you have the space and money, and if it's not too heavy for you. Keep in mind you will get stronger and there's much more upside in an Olympic bar than a standard one.
Do you need to use a barbell to get stronger? Definitely not! You can use other forms of weights (such as dumbbells or kettlebells), resistance bands, machines, or even your own body weight. But the barbell is a simple, time-tested tool for building strength. Despite its simplicity, there are many facets to safe and effective use (such as good form, exercise selection, how many reps and sets to do, how much weight to use, etc.) so finding a competent coach to get you started is highly recommended.
Now go get stronger! Be seeing you.