From Crocheting Bedspreads:
Single size - 16 balls
Double size - 21 balls

Milward’s steel crochet hook no. 7 or 8
Gauge: 7 bls or sps make 2”; 7 rows make 2” Each block measures about 9” square.

For a single size spread about 71 x 107 inches, including a 4” fringe all around, make 7 x 11 blocks.

For a double size spread, about 89 x 107” including 4” fringe, make 9 x 11 blocks