Most professional Occupational Therapists
recommend 10 to 12% of the user's weight.
30 to 39 pounds - 3 to 5 pounds
40 to 49 pounds - 4 to 6 pounds
50 to 59 pounds - 5 to 7 pounds
60 to 69 pounds - 6 to 8 pounds
70 to 79 pounds - 7 to 9 pounds
80 to 89 pounds - 8 to 10 pounds
90 to 99 pounds - 9 to 11 pounds
100 to 109 pounds - 10 to 12 pounds
110 to 119 pounds - 11 to 13 pounds  
120 to 129 pounds - 12 to 14 pounds
130 to 139 pounds - 13 to 15 pounds
140 to 149 pounds - 14 to 16 pounds
150 to 159 pounds - 13 to 17 pounds
160 to 169 pounds - 16 to 18 pounds
170 to 179 pounds - 17 to 19 pounds
180 pounds and up - 18 to 20 pounds
How do I decide how much weight?
We at Salt Of The Earth Weighted Gear are not Professional Occupational
Therapists. The advice we offer is based on recommendations offered by most OT's.
It is important that you get the recommendation of  your own OT.

The amount of weight you put into a vest should not be over 8% of the user's weight or
more weight than the user can comfortably carry for an hour. Your OT should help you
decide.

4 Reasons we don't make blankets over 20 pounds

1...
Once a person reaches adulthood, or around 150 pounds, their bone structure will
not change much, no matter how much they come to weigh. So a 15 pound blanket is
often sufficient for any size adult. For those needing extra weight, a 20 pound blanket
offers a very effective amount of pressure.
2... An extra heavy weighted blanket can be surprisingly awkward to handle.  Folded,
a 20 pound blanket is much like holding two 10 pound sacks of potatoes and the user
should be able to lift and carry it. Spread over the body, it is very comforting, but not
very easy to manipulate. Unfolded, it is a dead weight, like a small child who is not too
heavy until he/she goes limp in your arms. So if you want to readjust it in the night,
you'll be glad it's not more than 20 pounds.
3... Though our blankets are machine washable, 20 pounds is the maximum we feel
would be safe in the average washing machine.   
4....We feel that though our blankets are well constructed, with 4 layers of fabric, over
20 pounds could put too much strain on the stitching when the blanket is being pulled
around and manipulated.
: If you still want more weight, we suggest that you purchase two blankets to use
together. If you wanted 30 pounds, you could buy two 15 pound blankets or a 20
pound blanket an a 10 pound blanket.
How Much Weight Should I Put into my Weighted Blanket?