How to Find your Condom Size
Uh hey, to the folks out there who're being genuine when they say a condom is uncomfortable---you are likely either wearing the wrong size, or experiencing an allergy.
People focus a lot on length when it comes to condom size, but actually girth--how big around your dick is--is usually the main factor for why someone may be uncomfortable wearing an external condom.
How to measure your penis for a condom:
Grab either a measuring tape (preferably one that you can sterilize before and after this little endeavor), or a piece of string/yarn and a ruler. (if you use the string, you'll hold it up to your penis, pinch the string at the "measuring point," then measure the string against the ruler)
Measure Length by holding your measuring tool from the base of your erect penis to the tip of your penis (Most condom lengths should accommodate most penis sizes, as having there be some extra condom not unrolled by the time you reach the base of your dick won't make the condom less effective)
Measure your girth. Wrap your measuring tool around your erection. Some guides suggest doing this at the middle, but I recommend doing this at the widest point of your penis shaft as that will likely be the place you're finding discomfort if things feel too tight. Don't use your head measurement though! Most condom brands expect the head to be a bit larger than the shaft and will make room to accommodate that. If your head is particularly big, there are condom brands that offer extra room at the tip.
Look up a condom size chart. Ripnroll . com has a pretty extensive chart with measurements and photos. You should find it if you search "Ripnroll Condom Size Chart" in your search engine of choice (not linking because tumblr)
Acquire some condoms (consider getting a variety pack if you're still unsure) and try them out by yourself or with a partner you feel comfortable with.
When you put on a condom, it should fit snugly against you. Snug in this case means their shouldn't be loose material bunching up along your shaft, but also it should feel comfortable to wear for longer periods.
If the condom is loose and bunchy that's an indication you may need a narrower condom. A condom that's too loose may slip off, tear, or cause you and your partner chafing during sex.
If you struggle to keep an erection or feel like you're being pinched around the base of your shaft after a few minutes wearing a condom that's an indication you need to size up.
If your skin starts to itch/burn after wearing a condom, you may be allergic to either latex, the lubricant the condom uses, or the powder on the inside of the condom.
If you feel itchy after touching latex gloves and tend to get red outlines after wearing latex bandaids, you probably have a latex sensitivity and should try switching to a non latex condom variety.
If you typically have no bad reaction to latex in other contexts, and don't want to immediately switch to nonlatex condoms (they can be more expensive, unfortunately), try switching condom brands and see if that solves the irritation problem. If it doesn't, then do try non-latex. The skin of our genitals is more sensitive than other parts of our bodies, so if we are allergic to a material we're more likely to have a contact reaction there.
Condoms are a measure to make sex safer, not uncomfortable! When worn, they should ideally blend into the background during sex, not be such an overpowering feeling that you can't be present with your partner.
If condoms cause you discomfort even after sizing up, check with your local clinic, it could be a sign of something up.