The beauty of the granny square is you can work it in any yarn weight. I usually use worsted or light worsted yarn (aran or DK for UK folks) and a H size (5mm) crochet hook.
The instructions below are for the first three rounds. Repeat the instructions for round 3 on further rounds – you can keep on going until your square is massive!
The pattern is in US terminology.
Free Granny Square Pattern:
With Color A, ch4 and join to form a ring.
ch 1, sc, ch 2 (counts as 1dc), 2 dc, ch 2, [3 dc, ch 2] three times. Join in 2nd ch of first dc. End Color A.
Join Color B in any ch2sp, ch 1, sc, ch 2 (counts as 1dc), 2 dc, ch 2, 3 dc, ch 1 all in same ch2sp. [ In next ch2sp work 3 dc, ch 2, 3 dc, ch 1.] Rep [ to ] in each ch2sp. Join to first dc of round. End Color B.
Join Color C in a corner ch2sp, ch 1, sc, ch 2 (counts as 1 dc), 2 dc, ch 2, 3 dc all in same ch2sp. [ In each ch1sp work (3 dc, ch 1). In each ch2sp work (3 dc, ch 2, 3 dc, ch 1)]. Rep [ to ] around. Join to first dc of round. End Color C.
Repeat Round 3 for as many rounds as you want.
Hope you enjoy crocheting my free granny square pattern!