To me, business casual for men’s outfits is a loose definition, but it definitely has an upper and lower range of what’s appropriate. The only true way to determine what it means is by looking at it in relation to the current dress code of the company or function you’re dealing with.
Things to avoid in business casual
Ties
There are rare exceptions, but when in doubt, go without.
Shorts
These are too casual no matter how they’re worn and I’d argue that a man shouldn’t wear shorts in 95% of situations, anyways.
T-Shirts
While I love them, they have no place in a business casual outfit.
Not Tucking In Your Shirt
The sin of all sins for a business casual outfit, no matter your body type, is not tucking in your collared shirts. Polo shirts should only be worn untucked, but the exact opposite is true for collared shirts. It just looks sloppy.
Now let’s go over the typical outfits and when they’re appropriate to wear.
Standard Business Casual
For most companies, whether they require a suit (maybe no tie) or a blazer or collared shirt everyday, there are two types of business casual outfits. How close the dress code is to a full suit will determine whether you should wear a jacket or not. Also, depending on the time of year, you may go for lighter or heavier weighted fabrics for your jackets and pants. Hotter = lighter.

With A Jacket
If you are required to wear a suit and tie everyday, definitely go with this one.
Here’s another article I wrote about heavier sport coats/blazers for the Fall & Winter months. Please, whatever you do, don’t wear a suit jacket in place of this. The fabric is too thin and it won’t match the fabric weight of the pants you’ll be wearing.
Make sure either of these are tucked in to your pants. Definitely wear a belt that matches your shoe color, as well.
The more formal the dress code, the more likely you should wear wool trousers. Chinos are a little less formal or more used during spring and summer, while jeans a little less so than chinos and typically used year-round. Never, ever – unless the suit pants are a very thick wool (similar to wool trouser weight) – should you wear suit pants without the accompanying jacket.
The second you’re not wearing a full suit and tie, you can basically wear anything but sneakers with your business casual outfit. I’d default to Oxfords, Monk Straps or Loafers – either in suede or leather, but any of the options above are acceptable.

Without a jacket
If the dress code or occasion is slightly more casual, you can forgo the jacket and wear this business casual outfit, instead. There’s a few small points to consider.
If the weather is too warm, then definitely swap out the sweater for a blazer from the previous section, or, if it can be more casual, go to the next outfit, instead.
Shirt
Same as the previous outfit. You can wear a tie, like in the above picture, but it’s not necessary at all.
Pants
Wool trousers or dark wash jeans. Chino pants have a fabric weight that is too light to go well with v-neck sweaters.
Shoes
Same as previous outfit.
Casual Business Casual
This type of business casual outfit is appropriate if there’s a pretty casual dress code normally, or the event is very informal. If you see “business casual” as a requirement anywhere, this is the least formal outfit you can wear that is still appropriate for the dress code. Anything less than this is not business casual.

This is one of my favorite jackets of all time and fits this outfit perfectly. Obviously, only wear this if the weather is requiring a jacket.
I’d probably default to a polo shirt unless you knew for a fact you were going to wear the Harrington Jacket or the weather is cooler. Unless you’re a slimmer guy, an Oxford Button Down worn without a jacket on top of it doesn’t look too good. No matter what, though, make sure the polo shirt fits like a glove or you’re going to look like a goofball and if you wear the oxford, please tuck it in.
Chino pants are the default in an outfit like this, but dark wash jeans are just as appropriate. I’d let the time of year or weather dictate whether I went with chinos or dark wash jeans. The colder it is, the more I’d lean toward wearing the jeans over the chinos.
The more classy you want to make this casual outfit, the more I’d learn toward dressy shoes.
That’s it! Hope this is helpful!