Enter your room dimensions below and get an instant materials list for your drywall project — sheets, joint compound, tape, screws, and corner bead all calculated in real time. Deduct doors and windows so you buy what you actually need, not what you hope is close enough.
Pro tip: Hang drywall horizontally on walls, not vertically. Horizontal installation reduces the total linear feet of joints you need to tape and creates stronger mid-wall seams that are easier to finish flat.
How to Use the Drywall Calculator
Start by entering the room length, width, and ceiling height. The calculator immediately computes wall area and, if toggled on, ceiling area. Add doors and windows to deduct their openings from the total — standard presets are loaded automatically, but you can type in custom dimensions for non-standard openings like French doors or picture windows. Choose your sheet size, adjust the waste factor to match your experience level, and the full materials list updates in real time.
Choosing the Right Sheet Size
Drywall sheets come in three common lengths: 8, 10, and 12 feet, all 4 feet wide. The single most important decision is matching sheet length to your ceiling height. A standard 8-foot ceiling pairs perfectly with 4x8 sheets hung horizontally — two sheets stacked cover the wall with one horizontal seam at the midpoint. If your ceilings are 9 or 10 feet, a single 4x10 sheet hung horizontally eliminates that midwall seam entirely on the upper course, reducing taping time by roughly 20%. Twelve-foot sheets are ideal for tall ceilings and long unbroken runs, but they weigh about 90 pounds each for standard half-inch and require at least two people to handle safely.
Understanding Joint Compound Coverage
Joint compound, commonly called mud, is applied in three separate coats: one taping coat to embed the paper tape, and two finishing coats that feather the joints smooth. A gallon of pre-mixed joint compound covers approximately 100 square feet of flat joint per coat. The calculator estimates total compound needed across all three coats, then adds a buffer because butt joints, inside corners, and screw dimples consume more material than the flat seams between tapered edges.
For beginners, pre-mixed all-purpose compound is the easiest to work with — it has a longer working time and sands smoothly. Experienced finishers often prefer setting-type compound (sold as a powder you mix with water) for the taping coat because it hardens chemically rather than by drying, which means you can apply the first finish coat the same day without waiting overnight.
Screw Spacing: Walls vs. Ceilings
Building codes and manufacturer specifications differ between wall and ceiling fastening. On walls, screws are placed every 16 inches along each stud in the field (the middle of the sheet) and every 12 inches on the edges where two sheets meet. On ceilings, gravity works against you, so screws are spaced more tightly — every 12 inches on both edges and field joists. This calculator uses those standard spacings and accounts for the number of studs and joists your sheets will cross based on 16-inch on-center framing.
Waste Factor Guidelines
No drywall project uses 100% of the material purchased. Every cut-off piece shorter than about 16 inches is unusable, and odd-shaped walls, soffits, and offset windows generate more scrap. Industry standard waste allowance is 10% for simple rectangular rooms with few openings. Bump it to 15% for rooms with multiple windows, closet alcoves, or angles. First-time hangers should use 20% to account for learning-curve mistakes like snapping sheets in the wrong place or overdriving screws through the paper face.
Corner Bead: Inside vs. Outside
Outside corners — where two walls form an outward-pointing edge — require rigid corner bead to create a straight, durable edge that resists dents and impacts. Metal corner bead is the traditional choice; vinyl and paper-faced options are gaining popularity because they resist rust and are easier to finish. Inside corners are typically finished with paper tape folded along its center crease, which is simpler and does not require rigid bead. However, some professionals install no-coat inside corner bead for perfectly straight results in high-visibility areas like hallways or above kitchen cabinets.
Moisture-Resistant and Fire-Rated Boards
Standard white-face drywall works in most living spaces, but building codes require specialized boards in certain locations. Moisture-resistant drywall (green board) has a water-repellent paper face and a treated core that resists mold growth. It belongs behind tile surrounds in bathrooms, laundry rooms, and kitchens — though it should never be used on ceilings above showers, where cement board is required. Fire-rated drywall (Type X, 5/8-inch thick) contains glass fibers that slow the spread of fire through a wall assembly. It is required on walls and ceilings between an attached garage and living space, in furnace rooms, and in multi-family separation walls. Always check your local building code before buying — using the wrong type can cause a failed inspection and require you to rip it all out and start over.
Planning a broader home improvement project? Use the Paint Calculator to estimate primer and paint after your drywall is hung and finished. Browse all Home & Real Estate tools for more project planners.