Drywall Thickness Guide

Choosing the right drywall thickness depends on where it's going — standard walls, ceilings, garages, and wet areas all have different requirements. Here's the complete reference.

Thickness by application

Thickness	Type	Best for
¼ inch (6mm)	Flex board	Curved walls only
⅜ inch (9.5mm)	Standard	Patching, thin applications
½ inch (12.7mm)	Standard	Most interior walls and ceilings
½ inch	Sag-resistant	Ceilings with 24” joist spacing
5/8 inch (15.9mm)	Type X	Garage walls, fire-rated assemblies
½ inch	Moisture-resistant	Bathrooms, laundry rooms
¼ inch cement board	Backer	Behind shower tile

Application guide

Location	Recommended thickness	Notes
Interior walls	½”	Standard for all walls
Ceiling (16” OC joists)	½”	Can also use ½” sag-resistant
Ceiling (24” OC joists)	½” sag-resistant	Prevents sagging
Garage walls (to house)	5/8” Type X	Fire code requirement
Bathroom walls	½” MR (green board)	Not for wet areas
Behind shower tile	¼” cement board	Waterproof backer required
Curved walls	¼” flex drywall	Bend to shape; install in layers

Drywall types

Type	Description
Regular (whiteboard)	Standard ½” for most applications
Moisture-resistant (MR)	Green or purple face; for humid rooms
Type X (fire-rated)	5/8”; 1-hr fire rating; required for garages
Type C	Enhanced fire resistance; used in commercial
Soundproof (STC)	Denser core; reduces sound transmission
Sag-resistant	Extra-dense; for horizontal ceiling applications
Flex	¼” thin; for curved/arched walls

Sheet sizes and coverage

Sheet size	Square feet	Common use
4×8 ft	32 sq ft	Standard walls
4×9 ft	36 sq ft	9-foot ceilings
4×10 ft	40 sq ft	10-foot ceilings
4×12 ft	48 sq ft	Reduces seams; large rooms

Use the Drywall Calculator to get the exact sheet count for your room.

Fasteners and coverage

Screws: 1-1/4” Type S screws for ½” drywall, 1-5/8” for 5/8”
Nails: Not recommended — screws resist popping
Screws per 4×8 sheet (walls): approximately 28–32 screws
Joint compound (mud): roughly 1 gallon per 100 sq ft of drywall for tape and finish coats

Frequently Asked Questions

What thickness drywall should I use for walls?

½ inch (5/8" for fire-rated) is standard for most interior walls. Use ⅜" only for curved walls or patching. Ceiling drywall is also ½" with ½" sag-resistant panels for long joist spans.

What is the difference between ½" and 5/8" drywall?

½" is the standard for residential walls. 5/8" (Type X) provides a one-hour fire rating and is required between an attached garage and living space, or in commercial buildings. It is also heavier and more impact-resistant.

How many sheets of drywall do I need?

Each 4×8 sheet covers 32 square feet. Divide your total wall area by 32, then add 10–15% for waste and cuts. Use our Drywall Calculator for rooms with multiple walls and openings.

What size drywall sheets are available?

Standard sheets are 4 feet wide and come in 8, 9, 10, and 12 foot lengths. The most common is 4×8 (32 sq ft). 4×12 sheets are used to reduce seam count on tall walls or ceilings.

Do I need moisture-resistant drywall in bathrooms?

Yes — use moisture-resistant (MR) or greenboard in bathrooms and laundry rooms, especially near showers. Behind tile, use cement board or waterproof backer board instead.