This is my go to pattern when i need to make an adult beanie quickly. It fits most adult head sizes 21"-24" and it can easily be adjusted or customised.

Stitches will be in US terms otherwise general crochet knowledge is assumed.

Magic loop - Crochet cast-on

ch - Chain

dc - Double crochet

FPdc - Front post double crochet

BPdc - Back post double crochet

Step 1: Gather Supplies

For this pattern you'll need:

-a 4.5mm hook

-Fingering (4ply) weight yarn

-Yarn needle (tapestry needle)

-Scissors

Step 2: Getting Started and Increase Rounds

Pattern Note - at the end of every round slip stitch back into the first stitch to complete.

Start with 10 dc into a magic loop, pull loop tight. (If you don't understand magic loop just start with a ch3 joined to work in the round instead)

2nd to 8th round - dc in each, evenly increasing by 10 dc in each round (I stagger my increases for a rounder base, but it's not required knowledge to make the hat)

You should have 80 dc in your last round.

Step 3: Body and Ribbing

9th to 14th rounds - dc in each stitch

15th to 19th rounds - ch1, *FPdc, BPdc* rpt till end

Step 4: Finishing

And that's pretty much it finish off and weave in your ends and your new hat is ready to wear.

I usually give my finished pieces a soak in some wool wash before i'm done. I recommend it, but it's not a requirement.

You can also see in the pics i've attached that i've made a couple variations to show what you could do. The blue and red one was just a simple colour variation on the basic pattern but the green and grey hat is from my personal collection and was made to hold my messy dreads. I started with 12 increase rounds instead of 8 (120 stitches around) I made the body a bit deeper... I think it was about 12 rounds instead of 6, then had to add a few decrease rounds so i could get back to 80 stitches before the ribbing.