Drywall Calculator
Work out exactly how many sheets of drywall (sheetrock) you need to finish a room. Enter your room's length, width, and height, subtract the doors and windows, and this calculator turns the net wall and ceiling area into a panel count and total material cost — instantly.
It handles sloped walls, optional ceiling coverage, waste allowance, and any of the four standard US panel sizes, so you can walk into the store with the right number the first time.
- Includes doors & windows
- Sloped-wall support
- Panel & cost estimate
- Free, no signup
Drywall Calculator
What Is Drywall (Sheetrock)?
What it's made of, why it replaced plaster, and where it should never be used.
Definition and history
Drywall — also called plasterboard, wallboard, gypsum panel, or sheetrock — is a construction panel made of gypsum compressed between two sheets of paper. Its modern form took off during the mid-20th century, when building costs were high and skilled plastering labor was scarce; drywall's low price and easy installation made it the practical alternative, and it has been the standard way to finish interior walls and ceilings ever since.
Why builders prefer drywall over plaster
Unlike wet plaster, drywall needs no drying time — panels are cut to size, then nailed or screwed directly onto studs, so an experienced installer can finish an entire house in a matter of days. Damaged or dirty sections are simple to replace: cut out the faulty panel and screw in a fresh one, without redoing the whole wall.
Where not to use standard drywall
Standard drywall is not water-resistant. In kitchens, bathrooms, and other consistently humid spaces, ordinary panels soften and break down over time. Moisture-prone rooms call for a water-resistant panel, cement board, or tile instead.
Types of drywall sheets
- Regular drywall — plain white panels available from a thin ¼" (6.5 mm) up to a thick ¾" (20 mm), suited to most interior walls and ceilings.
- Greenboard drywall — identified by its green paper facing, treated to resist moisture; a common choice for kitchens and other humid rooms.
- Blueboard drywall — similar to greenboard but also mold-resistant, with a distinctive blue facing; typically more expensive than greenboard.
- Soundproof drywall — enhanced with damping polymers that absorb sound between rooms.
- Fire-resistant drywall (type X and C) — reinforced panels designed to slow the spread of fire, covered in detail below.
Drywall that will save you from fire
Gypsum, the core material in drywall, contains a surprisingly high proportion of water bound into its crystal structure. When drywall is exposed to fire, that water is released and evaporates in a process called calcination — and because evaporation absorbs a large amount of energy, it takes real time for flames to burn through a drywall layer, giving occupants extra time to escape. Type X drywall adds glass fibers that keep the panel from cracking as the water escapes, while type C combines those fibers with vermiculite, a mineral that expands under heat to seal emerging cracks. Fire-resistant drywall is a smart investment on walls shared with a garage or a furnace room.
Drywall sizes and thickness
The most common US drywall sizes are 4' × 8', 4' × 9', 4' × 10', and 4' × 12', while metric markets typically stock 1200 × 600 mm, 1200 × 2000 mm, 1200 × 2600 mm, and 1200 × 3000 mm sheets. Larger panels cover more area per sheet and finish a job faster, but they're heavier and harder to maneuver — smaller sheets are easier to handle in tight rooms. For thickness: ¼" and ⅜" (about 6.5 mm) panels suit ceilings and curved surfaces; ½" (12.5 mm) is the standard choice for typical walls; anything over ⅝" (15 mm) is used where extra sound or fire resistance is the goal.
How much does a sheet of drywall cost?
Sheetrock prices in the US typically fall between $6 and $15 per sheet, scaling with size: 4' × 8' sheets run about $6–$8, 4' × 9' about $9–$11, 4' × 10' about $10–$12, and 4' × 12' about $10–$14. Thicker panels and specialty types — water-, sound-, or fire-resistant — cost more than standard sheets.
Drywall tools and materials checklist
- Drywall mud (joint compound) — joins panels and covers holes; available dry, premixed, or low-dust.
- Drywall tape — paper or self-adhesive fiberglass tape that reinforces joints between panels.
- Drywall corner bead — plastic or metal edging that protects and finishes outside corners.
- Drywall screws — the modern standard fastener, since screws resist popping out over time better than nails.
- Drywall T-square — keeps cuts straight and panels correctly aligned.
- Drywall saw — cuts panels to fit irregular openings; manual or electric.
- Cordless drill or drywall screw gun — drives screws quickly and consistently.
- Drywall knife — smaller knives for slopping and taping, larger ones for feathering and finishing.
- Sanding pole or sponge — for the final smoothing pass, with poles helping reach higher walls.
How Much Drywall Do I Need?
The measurements this calculator uses, and how they turn into a panel count.
Room Dimensions
Enter the length, width, and height of your room, and choose whether to include the ceiling.
Doors, Windows & Slopes
Add door and window counts and sizes, plus any sloped-wall triangles, so they're subtracted or added correctly.
Net Surface Area
The calculator subtracts openings from the gross wall and ceiling area to find exactly how much surface needs covering.
Panels & Total Cost
Pick a panel size and cost, and get the number of sheets to buy — with an optional 10% waste allowance — and the total price.
Drywall Formulas
How gross area, net area, sloped-wall area, and panel count are calculated.
Gross Room Area
The wall area comes from the room's perimeter times its height; the ceiling area, if included, is simply length times width.
Sloped-Wall Area
Each triangular space under a sloped ceiling is measured like any triangle — base times height divided by two — then multiplied by how many identical sloped areas the room has.
Net Room Area
Subtracting the total area of doors and windows from the gross (plus sloped) area gives the actual surface that needs drywall.
Total Cost
Once the panel count is rounded up to a whole number of sheets, multiply by the price per panel to get the total material cost.
Worked Examples
Step-by-step drywall estimates for common room scenarios.
Example 1 — Basic Rectangular Room
A room is 12 ft × 10 ft with an 8 ft ceiling, no ceiling drywall, no doors or windows.
Example 2 — Including the Ceiling
Same room as Example 1, but the ceiling will also be drywalled.
Example 3 — Subtracting a Door and a Window
Using the 472 sq ft gross area, subtract one door (3 ft × 6.83 ft) and one window (3 ft × 4 ft).
Example 4 — Panels Needed (4' × 8' sheets)
Using the 439.5 sq ft net area from Example 3, with 4' × 8' panels (32 sq ft each).
Example 5 — Adding 10% Waste Allowance
Applying the recommended 10% waste allowance to the 439.5 sq ft net area before dividing by panel size.
Example 6 — Sloped Attic Wall
A converted attic room has two identical sloped-wall triangles, each with a 10 ft base and a 3 ft height.
Example 7 — Total Material Cost
Buying 16 panels of 4' × 8' drywall at $8 per sheet.
Quick Reference Tables
Standard drywall sizes, prices, and where different types are used.
| US Panel Size | Area | Typical Price |
|---|---|---|
| 4' × 8' | 32 sq ft | $6 – $8 |
| 4' × 9' | 36 sq ft | $9 – $11 |
| 4' × 10' | 40 sq ft | $10 – $12 |
| 4' × 12' | 48 sq ft | $10 – $14 |
| Metric Panel Size | Area |
|---|---|
| 1200 × 600 mm | 0.72 m² (≈7.75 sq ft) |
| 1200 × 2000 mm | 2.4 m² (≈25.83 sq ft) |
| 1200 × 2600 mm | 3.12 m² (≈33.58 sq ft) |
| 1200 × 3000 mm | 3.6 m² (≈38.75 sq ft) |
| Drywall Type | Best Used For |
|---|---|
| Regular | Standard interior walls and ceilings |
| Greenboard | Kitchens and moderately humid rooms |
| Blueboard | Bathrooms and mold-prone areas |
| Soundproof | Shared walls, media rooms, offices |
| Type X / Type C | Garage walls, furnace rooms, fire-rated assemblies |
Benefits of Using This Drywall Calculator
Why DIYers and contractors use a dedicated estimator instead of guessing.
Accurate Net Area
Automatically subtracts doors, windows, and adds sloped-wall triangles for a true surface count.
All Standard Panel Sizes
Covers every common US size plus four metric sheet sizes used internationally.
Built-In Waste Allowance
An optional 10% buffer accounts for cuts, mistakes, and future repairs so you don't run short mid-job.
Instant Cost Estimate
Enter a price per sheet and see the total material cost the moment you calculate panels.
Sloped-Wall Support
Handles attic conversions and rooms with angled ceilings without manual triangle math.
Mobile-Friendly
Works just as well on a phone at the hardware store as on a desktop while planning.
Where Drywall Estimating Matters
Real projects that depend on getting the panel count right.
New Home Construction
Estimating whole-house sheetrock needs room by room before ordering material.
Basement Finishing
Calculating drywall for framed basement walls and ceilings, often including moisture-resistant panels.
Garage Conversions
Sizing fire-resistant Type X drywall for walls shared with living spaces.
Attic Renovations
Using sloped-wall calculations to cover angled ceilings under the roofline.
Kitchen & Bathroom Remodels
Planning moisture- or mold-resistant greenboard and blueboard panel counts.
Home Offices
Adding soundproof drywall to reduce noise transfer between rooms.
Rental Property Repairs
Estimating replacement panels for damaged sections between tenants.
Commercial Fit-Outs
Budgeting sheetrock for office partitions and interior build-outs.
DIY Renovation
Avoiding costly extra store trips by ordering the right quantity up front.
General Contracting
Quoting material costs accurately across multiple rooms in a bid.
Insurance Restoration
Estimating drywall replacement after water or fire damage.
Workshop & Garage Builds
Covering utility spaces with standard or impact-resistant panels.
Common Drywall Estimating Mistakes
Avoid these classic errors before you place a material order.
Forgetting to subtract doors and windows
Using the full gross wall area without removing openings leads to over-ordering material and overestimating labor.
Skipping the waste allowance
Cuts, mis-measurements, and future repairs typically consume about 10% extra material — leaving no buffer risks a mid-project shortage.
Measuring room height to the roofline instead of the sloped-wall base
In attic rooms, wall height should be measured only to where the slope begins, with the triangular space calculated separately.
Mixing metric and imperial measurements
Combining a room measured in meters with panel sizes listed in feet without converting first produces an incorrect panel count.
Rounding down the panel count
Panels can only be bought as whole sheets, and rounding down leaves part of a wall uncovered — always round up.
Using standard drywall in wet areas
Installing regular panels in kitchens or bathrooms instead of moisture-resistant greenboard or blueboard leads to early failure.
Frequently Asked Questions
Direct answers to the questions people ask most about drywall estimating.
What is drywall (sheetrock)?
Drywall, also called plasterboard, wallboard, gypsum panel, or sheetrock, is a panel of gypsum compressed between two sheets of paper, used to finish interior walls and ceilings without the drying time plaster requires.
How many sheets of drywall do I need for a room?
Calculate the gross wall (and ceiling, if included) area, subtract the area of doors and windows to get the net area, then divide by the area of one panel and round up to the next whole sheet.
How do I calculate the area under a sloped wall?
Measure the base and height of the triangular space beneath the slope and apply the triangle area formula: area = base × height ÷ 2. Multiply by the number of identical sloped sections in the room.
Should I include the ceiling when calculating drywall?
Only if you're drywalling the ceiling too. Toggle the ceiling option on to add length × width to the gross area, or leave it off to calculate walls only.
How much extra drywall should I buy for waste?
A common rule of thumb is 10% extra, to cover cutting waste, mistakes, and future patch repairs.
What size drywall sheets are available?
The most common US sizes are 4' × 8', 4' × 9', 4' × 10', and 4' × 12'. Metric markets typically use 1200 × 600 mm, 1200 × 2000 mm, 1200 × 2600 mm, and 1200 × 3000 mm sheets.
How much does a sheet of drywall cost?
In the US, sheetrock typically costs $6 to $15 per sheet depending on size and type, with larger and specialty panels (fire-, water-, or sound-resistant) costing more.
What's the difference between greenboard and blueboard drywall?
Both resist moisture, but blueboard also resists mold and costs more than greenboard. Greenboard suits moderately humid rooms like kitchens; blueboard suits wetter areas like bathrooms.
Can I use regular drywall in a bathroom?
No. Standard drywall isn't water-resistant and will soften in humid conditions — use greenboard, blueboard, cement board, or tile instead.
What makes drywall fire-resistant?
Gypsum contains bound water that evaporates when exposed to fire, absorbing heat and slowing the flame's progress. Type X drywall adds glass fibers to prevent cracking; type C adds vermiculite, which expands to seal cracks under heat.
What tools do I need to install drywall?
Drywall mud, tape, corner bead, screws, a T-square, a drywall saw, a screw gun or cordless drill, a drywall knife, and a sanding pole or sponge for finishing.
Can this calculator estimate the total cost of drywall?
Yes. Enter a cost per panel alongside your room measurements, and the calculator multiplies it by the number of panels needed for a total material cost.
What drywall thickness should I use?
¼" or ⅜" for ceilings and curved surfaces, ½" for standard walls, and over ⅝" where extra sound or fire resistance is needed.
Is this drywall calculator free?
Yes, it's free to use with no signup required.
Can I use this calculator on mobile devices?
Yes, the layout is fully responsive and works on phones, tablets, and desktops.
Ready to Order the Right Amount of Drywall?
Get an accurate panel count and total material cost for your room in seconds — no more guessing, no more extra trips to the store.