How to use this calculator
Start by entering your room's length, width, and ceiling height in feet. The calculator figures out the total wall area from the perimeter. Add the number of doors and windows so it can subtract those openings. Standard doors are counted at 21 sq ft and windows at 15 sq ft.
Toggle the ceiling option if you're drywalling the ceiling too. You can add multiple rooms to get a single material list for your whole project. Choose your sheet size (4×8 or 4×12) and adjust the price per sheet to match your local prices.
The calculator adds a 10% waste factor automatically to account for cuts, mistakes, and odd-shaped areas. It also estimates joint compound, tape rolls, and screws so you can buy everything in one trip.
Drywall types and thickness options
Not all drywall is created equal. The type and thickness you choose depends on where it's going and what it needs to withstand.
| Type | Thickness | Best for |
|---|---|---|
| Regular (white) | 1/2" | Standard interior walls and ceilings |
| Fire-resistant (Type X) | 5/8" | Garage walls, furnace rooms, code-required areas |
| Moisture-resistant (green) | 1/2" or 5/8" | Kitchens, laundry rooms, basements |
| Mold-resistant (purple) | 1/2" or 5/8" | Bathrooms, high-humidity areas |
| Soundproof (QuietRock) | 5/8" | Home theaters, bedrooms, shared walls |
1/2-inch vs 5/8-inch drywall
Half-inch drywall is the standard choice for most interior walls and ceilings in homes with 16-inch joist spacing. It's lighter, cheaper, and easier to handle, a 4×8 sheet weighs about 52 pounds compared to 70 pounds for 5/8-inch.
Five-eighths-inch drywall is required by most building codes on shared walls between garages and living spaces because it provides better fire resistance (Type X is rated for one hour). It also resists sagging on ceilings with 24-inch joist spacing and provides noticeably better soundproofing between rooms.
When in doubt, check your local building codes. Many jurisdictions require 5/8-inch Type X drywall in specific locations regardless of personal preference.
Frequently asked questions
How many sheets of drywall do I need for a 12×12 room?
A 12×12 room with 8-foot ceilings has 384 sq ft of wall area. After subtracting a door and two windows, you have about 333 sq ft. With a 10% waste factor, plan on 12 standard 4×8 sheets for the walls alone. Add 5 more sheets if you're doing the ceiling.
How much joint compound do I need per sheet of drywall?
Plan on one pre-mixed box (4.5 gallons) of joint compound for every three standard 4×8 sheets, or roughly one box per 100 square feet of drywall. This covers three coats of taping and finishing. Heavy texturing or skim-coating will require more.
Should I use 1/2-inch or 5/8-inch drywall?
Use 1/2-inch for most interior walls and ceilings with 16-inch joist spacing. Use 5/8-inch for ceilings with 24-inch spacing, garage-to-house walls (fire code), and anywhere you want extra soundproofing or fire resistance.
What size drywall sheets should I buy, 4×8 or 4×12?
Choose 4×8 sheets for most residential projects, they're easier to handle and fit through standard doorways. Use 4×12 sheets for rooms with taller ceilings or long walls to reduce the number of seams, which means less taping and a cleaner finish.