The best way to know how much you are feeding your horse is to buy a spring balance from a hardware shop, or your feed merchant, and weigh your feeds properly.

Saracen Horse Feeds have provided a helpful guide below which gives you a guide to the weight of most feeds when using a traditional round hand-scoop, filled level to the top (Image right).

N.B two different peoples scoop sizes (level or heaped) could produce a variation in weight as much as 50%.

RE-LEVE 1.1kg 2.24lbs
Enduro Performance 1.0kg 2.2lbs
Competition-Fit Mix 1.2kg 2.64lbs
Show Improver Mix 1.2kg 2.64lbs
Cooling Mix Plus Herbs 1.0kg 2.2lbs
Livery Mix 1.0kg 2.2lbs 
Donkey Diet 1.5kg 3lbs 4oz
Super Fibre Mix 0.6kg 1.32lbs
Veteran Mix 1.1kg 2.42lbs
Level-Grow™ Mix 1.3kg 2.86lbs
Stud Mix 1.2kg 2.64lbs
Mare-Care 1.1kg 2.42lbs
Stallion Plan 1.0kg 2.2lbs
Stud Prep 14 1.1kg 2.42lbs 
Saracen Cubes (Show Improver, Super Fibre etc) 1.5kg 3.3lbs
Saracen Molassed Chaff 0.3kg 0.66lbs
Canadian Oats 1.3kg 2.86lbs
Superioats 1.6kg 3.52lbs
Crushed Oats 1.2kg 2.64lbs
Sugar Beet Pellets - wet 2kg = 295gm DM 4lbs 10oz
Sugar Beet Pellets - dry 1.4kg 3lbs 
EQUI-JEWEL® (Dedicated measuring cup available) 0.25kg / cup 0.55lbs / cup