Half-Inch Drywall
This is the standard. When someone says drywall without specifying thickness, they mean half-inch. Most residential walls are half-inch.
Weight: About 1.6 pounds per square foot. A 4x8 sheet weighs around 51 pounds. Manageable for one person on walls, awkward but doable for short distances.
Use for: Standard walls with studs at 16 inches on center. Works for 24-inch spacing on walls but may flex slightly between studs.
Most of my house is half-inch drywall. It's adequate for walls where you're not trying to achieve anything special like fire rating or sound control. For normal living spaces, it's the right choice.
5/8-Inch Drywall
The heavy-duty option. Stiffer, heavier, and required in many applications.
Weight: About 2.2 pounds per square foot. A 4x8 sheet weighs around 70 pounds. Definitely harder to handle solo.
Required for: Ceilings in most codes, especially with 24-inch joist spacing. Fire-rated assemblies. Garages attached to living spaces. Any situation where sag resistance matters.
The extra thickness prevents ceiling sag that can happen with half-inch drywall over time. The weight and stiffness also provide better sound transmission reduction. Our master bedroom shares a wall with the living room, and when we replaced one side with 5/8-inch, the difference in sound transfer was noticeable.
Type X is the fire-rated version of 5/8-inch drywall. It contains glass fibers that help it resist fire longer. Required for garage walls adjacent to living spaces and in many commercial applications.
Quarter-Inch Drywall
Thin and flexible. Not for structural walls.
Weight: About 1.0 pounds per square foot. A 4x8 sheet weighs around 32 pounds. Easy to handle but flexes when carried.
Use for: Curved walls and archways. Covering damaged existing walls where you don't want to remove the old material. Sometimes for mobile home repairs where weight matters.
I've used quarter-inch exactly twice. Once to wrap a curved archway between our living room and dining room, which required wetting the sheets to bend them. Once to skim over a damaged plaster wall that would have been a nightmare to remove.
It's not strong enough for normal wall applications. You'd feel the flex if you pushed on it. But for specialty uses where you need to bend drywall or add a thin layer over existing surfaces, it works.
3/8-Inch Drywall
The forgotten middle child. Neither here nor there.
Weight: About 1.3 pounds per square foot. Lighter than half-inch, stiffer than quarter-inch.
Use for: I honestly rarely see it used. Some mobile home applications. Some remodel situations where half-inch is too thick but quarter-inch is too flexible.
I've never bought 3/8-inch drywall intentionally. My local Home Depot doesn't even stock it regularly. If half-inch doesn't work for your situation, you're usually better off with quarter-inch and proper backing rather than trying to find 3/8-inch.
Fire-Rated Type X
Fire rating is about containing fire to one area long enough for occupants to escape. Type X drywall is designed for this.
Type X means the drywall meets specific fire resistance standards. Typically 5/8-inch thick with glass fiber reinforcement that holds the gypsum core together longer under heat.
Required for: Garage walls and ceilings when attached to living space. Many commercial applications. Stairwell enclosures. Furnace rooms.
The exact requirements vary by code, but the principle is: if fire starts on one side, Type X buys time before it burns through to the other side.
When I finished our attached garage, Type X was required on the ceiling and the wall shared with the house. It's heavier and costs slightly more, but it's not optional where codes require it.
Lightweight Drywall
Some manufacturers offer lightweight versions of standard thicknesses. Half-inch lightweight might weigh 35-40 pounds per sheet instead of 50+.
The weight reduction comes from different gypsum formulations. Performance is similar to regular drywall for most purposes.
Advantages: Easier to handle, especially for ceilings. Easier on your body over a large project.
Disadvantages: Slightly more expensive. Some finishers say it sands differently and takes paint differently, though I haven't noticed major issues.
I've used lightweight for ceiling work when working alone. The reduced weight made a meaningful difference in fatigue over a weekend of installation. For walls where I have help, I go with regular weight to save the cost premium.
Sound Damping Drywall
Products like QuietRock and similar are designed specifically for sound control. They use viscoelastic layers or dense gypsum formulations to reduce sound transmission.
These can be more effective than just going thicker. A single layer of sound-dampened drywall might outperform double layers of regular drywall for sound control.
Cost is significantly higher. QuietRock can be $50+ per sheet versus $10-15 for regular drywall. Worth it for specific applications like home theaters, music rooms, or bedrooms adjacent to noisy spaces.
I haven't used it, but my neighbor installed QuietRock in his home office that shares a wall with his kids' playroom. He says it made a real difference in being able to concentrate during the day.
Choosing for Your Project
My decision process:
Standard walls: Half-inch unless you have a reason for something else.
Ceilings: 5/8-inch, always. The sag prevention is worth the extra weight and cost.
Garage adjacent to living space: Type X per code requirements.
Curved surfaces: Quarter-inch, doubled up if needed for rigidity.
Sound sensitive areas: Consider 5/8-inch for the mass, or specialized sound drywall if budget allows.
Don't overthink it. For residential work, 90% of what you install will be half-inch on walls and 5/8-inch on ceilings. The specialty thicknesses and types are exactly that, special cases.