Even a cheap kitchen cabinet should hold 30-to-50 pounds with no problems or failure. Purchased cabinets come with stated weight limits. The problem with checking your cabinets to determine their maximum weight load is by the time you determine that maximum weight limit you've weakened the cabinets. Unless you're filling your cabinets with bricks or cans of paint, even cheap cabinets will hold the average contents of a normal kitchen. If you plan on using the cabinets for tools, gallons of paint or chemicals or non-kitchen related items, invest in a better quality cabinet, or in solid wood shelving or cabinets.