A running cap has one job: to disappear. If you are thinking about it at kilometre eight, something about it is wrong. Most people arrive at the right cap by buying two or three wrong ones first, which is an expensive way to learn a short lesson. Here is how to get it right the first time.
Start with the measurement, not the size
Run a tape around your head just above the ears and across the middle of your forehead. S/M covers roughly 56.5 cm. M/L sits closer to 58 cm. If you land between the two, size up — a cap that is marginally loose can be adjusted, while one that is tight will leave a line across your forehead and a headache by the end of the week. Measure in the afternoon rather than first thing, and do not pull the tape tight; you want the number your head actually is, not the number you would like it to be.
Brim shape is a preference, not a hierarchy
A flat brim sits level and packs down flat, which matters if the cap spends half its life stuffed in a vest pocket. A curved brim wraps closer to the face and tends to stay put in a crosswind. Neither is faster. Try the one that looks like the caps you already reach for, because the cap you like the look of is the cap that will actually leave the house with you.
The band is the part that matters
Almost every complaint about a running cap is really a complaint about its headband. Look for a mesh band rather than a flat strip of fabric — it moves sweat sideways instead of straight down into your eyes, and it stays comfortable long after a woven band has gone heavy. This is also the part that determines whether a cap is still pleasant in humidity, which is where most caps quietly fail.
One honest caveat
Caps stretch. A new cap that feels perfect will feel slightly roomy in a month, which is why we would rather you start a touch snug than a touch loose. Not tight. Snug. If it leaves a mark on your forehead after ten minutes of standing still, it is too small, and no amount of wearing in will fix that.
Start with Everyday Caps if you want one cap for everything, or Low-Profile Caps if you prefer something that sits closer to the head.
