Adventurers carry a lot of gear. When that quantity becomes extreme, it might be enough to slow you down and otherwise hamper your capabilities. The amount you carry should rarely be an issue, and you don’t need to calculate the weight your character is hauling around unless it’s likely to matter. More often, you’ll need to know how much weight you can push or drag along the ground—are you strong enough to slide the statue covering the trapdoor? This information is contained in your Strength score. Multiply your Strength score by 10. That’s the weight, in pounds, that you can carry around without penalty.
This amount of weight is considered a normal load. Double that number (Strength × 20). That’s the maximum weight you can lift off the ground. If you try to carry that weight, though, you’re slowed. Carrying such a load requires both hands, so you’re not particularly effective while you’re doing so. This amount of weight is considered a heavy load. Five times your normal load (Strength × 50) is the most weight you can push or drag along the ground. You’re slowed if you try to push or drag more weight than you can carry without penalty, and you can’t push or drag such a heavy load over difficult terrain. This amount of weight is referred to as your maximum drag load. Your DM might rule that you can’t carry certain objects at full speed no matter what your Strength score is, just because they’re so bulky or unwieldy.
Your DM can also ask you to make a Strength check to push or to lift something heavy in a stressful situation, such as in the middle of combat.