The five common ratings
| Type | Duty description | Working load |
|---|---|---|
| IAA | Special duty | 375 lb |
| IA | Extra heavy duty | 300 lb |
| I | Heavy duty | 250 lb |
| II | Medium duty | 225 lb |
| III | Light duty | 200 lb |
The type is a load category, not a promise that one ladder is better for every use. A properly selected Type I ladder may be exactly right for one buyer; a Type III may leave too little margin for another.
Add everything going up
Start with body weight, then add clothing, boots, tools, paint, materials, and anything carried or supported. A 210-pound user with 15 pounds of clothing and tools already creates a 225-pound working load. The better comparison is to the total realistic load, with comfortable margin—not body weight alone.
Person: 210 lb + clothing and boots: 8 lb + tools and materials: 17 lb = 235 lb total. A 225 lb Type II rating is not enough; a Type I or higher rating fits the stated load.
Deciding between the two most common heavier categories? The 250-pound versus 300-pound comparison works through three realistic load calculations and two like-for-like six-foot models.
Rating is not the whole choice
Aluminum is often lighter and resists corrosion, but it conducts electricity. Fiberglass is commonly chosen when electrical hazards may be present, yet no ladder makes electrical work automatically safe. Type, material, length, setup, and condition all have to match the job.
Inspect the ladder label before every use. If a label is unreadable, a rail is damaged, a foot is missing, or a lock is unreliable, take the ladder out of service rather than guessing. For compact models, continue with the guide to telescoping-ladder locks and labels.
Rating reference: the ANSI A14.2 preview lists the working loads above for portable metal ladders. Always use the rating and instructions on the specific ladder.