Hudson's Bay Blanket Size Chart

Mattress Size Charts to Assist In Blanket Selection

Notes:
Some manufacturers are currently either adding a few extra inches OR shaving inches off of these "standard" sizes.
 

Also note that mattress depths vary widely by manufacturer.

Measure the depth of your mattress before purchasing blankets.

Standard and older mattresses average 9-12", while newer pillow-top mattresses are 14-16" deep and up. These deeper mattresses will require additional depth.
As you can see a full (4 point) Hudson Bay Blanket will cover the entire top of a queen size mattress but with less overlap around each size. This is fine for an extra warming blanket. Some people don't want a lot of overlap so they will purchase a smaller size blanket.

On the other hand a King (8 Point) Hudson Bay Blanket will give you lots of overhang on a Queen size Mattress if you want to tuck the blanket under the mattress.

It's all a matter of preference.