500 S&W Magnum This is the preeminent conceal carry caliber for anyone who absolutely wants to stop a threat. If you hit the bad guy right with this, he/she is sure to stop raping or carjacking. This caliber also works on barriers like car doors or human blubber. I recommend the 500gr XTP at 1425fps or if there are barriers where you live, the 700gr hardcast at 1200fps.
45-70 This is an excellent self-defense caliber that is capable of one-shot stops. You need to be strong to wield it but it can work. A 325gr JHP at 2000fps is a great place to start for a carry load.
454 Casull This caliber is sure to stop a mugger if you hit them center mass. I recommend the 300gr XTP at 1650fps
.44 magnum This is a good carry caliber and the bullet has enough mass and energy to stop a human threat. A 300gr JHP with lead exposed on the tips at 1300fps is a good carry load with this caliber.
.460 Roland This is the minimum caliber I would recommend for self defense for conceal carry. Although not as powerful as .44 magnum it can be used in a semiautomatic handgun so that is a plus (quicker shots). With judicious shot placement, a mugger can be stopped with a well-designed 230gr JHP at 1400fps
10mm This caliber is somewhat lacking but still has more. Due to the lower energy it is recommended to carry 220gr hardcast ensure penetration. It is also noted to maybe carry a 180gr JHP at 1300fps if you don't want the bad guy to die.
9mm, 45 ACP, .40
These are all calibers that are used by law enforcement, but really they are not powerful enough to reliably stop a threat. One possible use for them is if you have a small penis, telling the date you carry these will help them adjust their expectations. If you are just looking to defend yourself against a medium sized dog these are okay choices however.
.380 This caliber suffers from the same issues as the 9mm, but since it's even smaller, there are a small number of people who are so accurate like John Wick they can be effective with it, shooting assailants in the face. Also if you are a woman and limited to a boob holster this might be your only option for conceal carrying unless you get fake boobs to conceal a .460 Rowland.
.22lr This is a good way to either get rid of mice, or if robbers are wimps old grannies can try to scare them away with it. It's recommended to shoot for the balls since the .22lr bullet will bounce off a skull and will have trouble penetrating clothing
People I know who ccw mostly have .40 sig 229s or full-size sig 320s.
You did say concealed, after all.