The Complete Wood Screw Size Chart: Diameter, Length & Gauge Explained

Picking the wrong screw size is the fastest way to ruin an outdoor project. Too short and your deck boards cup within a season. Too thin and they snap in hardwood. This wood screw size chart maps the exact screw sizes for every outdoor project, based on 28 years of building decks, fences, docks, and other outdoor structures.

Each screw diameter chart below includes the gauge, length, pilot hole, and the exact screw most pros reach for. If you've ever wondered how to measure screw size or what gauge screw for decking, fencing, or framing, you're in the right place.

Jump to Your Project:

• Deck Screw Sizes
• Framing & Structural Screw Sizes
• Fence Screw Sizes
• Dock & Marine Screw Sizes
• Pergola, Gazebo & Shade Structure Screw Sizes
• Garden Beds, Planter Boxes & Outdoor Furniture
• Retaining Walls & Landscape Timber
• Sauna, Hot Tub & Pool Deck
• Treehouse, Playset & Outdoor Stairs
• #10 vs #12 Screws Explained
• #8 vs #10 Screws Explained
• Master Screw Size Chart by Project

Deck Screw Sizes: What Size Screw for Decking

The right deck screw size depends on your board thickness, wood species, and how close you are to saltwater. This decking screw sizes chart covers every common scenario, from 5/4 pressure-treated to composite and hardwood like ipe.

How to Pick the Right Deck Screw Size

Here's the quick version of this wood screw size chart for decks:

• What size screw for 5/4 decking? Go with #10 x 2-1/2". That gives you the full inch through the board plus 1.5" embedment depth into the joist. It's the most common deck screw size for a reason. Eagle Claw's 304 SS version runs $27.40/100-pack with a Type-17 point and Torx T25 star drive.
• What's the deck screw length for 2x6 boards? Step up to #10 x 3". Same 1.5" joist bite, just longer to get through the thicker board. One builder on a trades forum said it best: "Will they work? Yes. Will you regret it? Yes" about using 2-1/2" screws on 2x6 boards.
• How long should deck screws be? The rule is simple: screw length equals board thickness plus at least 1" to 1.5" of embedment depth into the joist. For 5/4 boards (1" actual), that's 2-1/2". For 2x boards (1-1/2" actual), that's 3".
• What size screw for deck boards in stainless? Stainless steel screws are softer than hardened carbon steel screws, so you want #10 gauge to make up for it. With hardened coated screws like Simpson DSV, #8 is fine for most 5/4 boards. We cover this more in our deck screw types guide.
• Pressure-treated wood? Only stainless steel screws or hot-dip galvanized fasteners. The copper in ACQ treated lumber eats through zinc-plated screws in a couple years. You'll pull them out as rusty shards.
• Composite decking? Don't use regular timber screws. They mushroom the composite around the head. Grab Starborn Cap-Tor xd or Simpson DCU.
• Hardwood like ipe? Pre-drill every single hole. Or save yourself the trouble and grab Simpson's DHPD with a paddle tip that drills its own hole as it goes. The wood screw diameter for ipe is still #10, but the shank needs a clearance hole at 3/16" to avoid splitting.
• Which Torx screw sizes for decking? Most deck screws use T25 Torx (star drive) bits. Shorter screws (#8 x 1-5/8") sometimes use T20. Torx resists cam-out way better than Phillips, especially in hardwood. Every Eagle Claw box includes a driver bit.
• Spacing: Two screws per joist per board, 3/4" to 1" from each edge. Boards wider than 6" get three screws to stop cupping. Figure roughly 350 screws per 100 sq ft. The Eagle Claw screw calculator gives you a quick count.

Framing & Structural Screw Sizes: What Size Screw for Framing

Structural connections are where screws can get dangerous if you pick the wrong size. Deck screws are hardened carbon steel that snaps clean under sideways shear force. Put one in a joist hanger and it can break without anyone seeing it until the deck gives way. Every framing screw size in this chart has a code evaluation report behind it.

Choosing the Right Screw for Structural Connections

Let me save you a headache (or worse). Here's your framing screw sizing guide:

• What size screw for joist hanger connections? Never put deck screws in joist hangers. About 40% of inspected decks get flagged for this. The only approved screw is the Simpson SD Connector (#9 x 1-1/2" or #9 x 2-1/2"). Nothing else passes inspection.
• What size screw for 2x4 framing? Simpson SDWS Framing at 0.160" x 3" replaces 16d common nails. Two per stud-to-plate connection. For a deeper dive, check our construction scre vs deck screw guide.
• What size screw for subfloor? Simpson WSV #9 x 2-1/2" at 6" on center at panel edges and 12" in the field. It's the only subfloor screw with full diaphragm-level code evaluation (ESR-1472).
• Ledger boards? Forget lag bolts. The Simpson SDWS Timber at 0.220" diameter does the same job without pre-drilling, a wrench, or washers. One 6" SDWS holds about 300 lbs of shear in Douglas Fir. Use the Simpson Fastener Designer to figure out your spacing.
• Know which Simpson screw goes where. SDWS Framing (0.160", T25) replaces framing nails. SDWS Timber (0.220", T40) replaces lag screw sizes like 1/2" lags. SDWH Timber-Hex (0.276", hex drive) is for heavy timber and marine. SD Connector (#9 or #10, hex drive) goes in metal connectors only. Mix them up and you'll get red-tagged.

Fence Screw Sizes: What Size Screw for Fence Pickets and Rails

Fence screws are smaller and shorter than deck screws because the stock is thinner and the loads are different. Splitting is the number one headache with wood screw sizes for fencing, especially in cedar.

Picking the Right Screw for Different Fence Styles

A few things I wish someone had told me before my first fence build:

• What size screw for fence pickets? Standard cedar pickets are only 5/8" thick. A #10 is overkill and will split them, especially near the edges. Drop to #8 x 1-5/8" and you get about 1" of embedment depth into the rail. That's plenty for a picket that mainly just has to stand up to wind.
• What size screw for fence rails to posts? #10 x 3" to 3-1/2", face-screwed. Contractors who've been at it 20+ years will tell you the same thing: face-screw your 2x4 rails to the 4x4 posts. Two per connection, staggered. Way stronger than toe-screwing.
• Stainless steel screws aren't optional on cedar. Cedar tannins react with anything iron-based and leave ugly black streaks you can't get off. Eagle Claw #8 x 1-5/8" 304 SS ($18.70/100-pack) with Type-17 point and star drive is the right call. Our cedar fencing guide goes deeper.
• Wire fencing? Cat's Claw Fasteners are a lifesaver. Each clip uses a #10 x 2" hex-head screw with a steel claw that holds 4x better than traditional staples and goes in 35% faster. Grab the softwood version for cedar, pine, or spruce posts.

Dock & Marine Screw Sizes

Docks take more punishment than any other outdoor project. Constant water, salt spray, wave action. Every single fastener has to hold up, because pulling apart a dock to swap out rusted screws is nobody's idea of a fun weekend. This section of the wood screw size chart covers freshwater and saltwater applications.

Why Docks Need 316 Stainless Steel Deck Screws

Think of it this way. Regular 304 stainless steel has a good shield against rust. 316 stainless steel has the same shield plus a backup layer. That backup is molybdenum (2-3%), and its whole job is to fight salt. We break this down in our 304 vs 316 stainless steel comparison.

• Saltwater dock or within about 3 miles of the coast? 316 SS on everything. IRC Section R507.2.3 requires stainless within 300 feet of a saltwater shoreline, but smart builders use 316 out to about 3,000 feet.
• Freshwater dock? Eagle Claw 304 SS works great and it'll last decades. For commercial docks, bump to 316 for extra peace of mind.
• Cleats and ladder brackets? Through-bolt with backing plates. A boat pulling on a cleat will yank a lag right out.

More in our dock and timber structures guide.

Pergola, Gazebo & Shade Structure Screw Sizes

Pergolas have two completely different fastener jobs: the heavy structural connections (posts, beams, rafters) and the lighter trim work (fascia, lattice, purlins). The screw gauge sizes are different for each, so don't grab the same box for both.

Fastening Overhead Structures Safely

Building something over your head means you want to get the fasteners right the first time:

• Post-to-beam joints are where most people overthink it. Simpson SDWS Timber screws (0.220" diameter, 5-6" long) toe-screwed at opposing angles is the modern fix. For big 6x6 posts, step up to the Simpson SDWH Timber-Hex at 0.276".
• Rafter hangers get Simpson SD Connector screws, same as joist hangers. Fill every hole. Within 5 miles of the coast, go 316 SS on the hardware.
• Trim, fascia, and lattice are the easy part. Eagle Claw #10 x 2-1/2" 304 SS handles all of it. The Torx T25 star drive is a lifesaver when you're working overhead because it won't strip out on you.

Our pergola construction guide walks through the full build process.

Garden Beds, Planter Boxes & Outdoor Furniture Screw Sizes

Lighter-duty outdoor projects where food safety, flush heads, and a clean look matter just as much as holding power. The #6 screw diameter (0.138") comes into play here for delicate trim and furniture slats, while #8 and #10 handle the structural joints.

Screws for Food-Contact and Finish Projects

If you're growing veggies, here's the good news: stainless steel screws are completely food-safe. Same material they make hospital instruments and commercial kitchen gear from. Eagle Claw 304 SS is the best pick for garden beds.

• Galvanized screws are fine for gardens too. Zinc is actually a nutrient your plants need, and the tiny amount from a handful of screws is hundreds of times less than what's already in your soil.
• Cedar garden beds need stainless. Tannins plus iron equals black streaks. Go stainless steel from day one and skip the headache.
• Countersink everything on furniture. Any surface people sit on or eat off should have flush heads. Eagle Claw's flat heads with nibs self-countersink in softwood. For hardwood furniture, pre-drill and countersink manually.
• Use carriage bolts for picnic table legs. Those joints carry full body weight. 3/8" carriage bolts with lock nuts are the right call.

Retaining Walls & Landscape Timber Screw Sizes

Retaining walls hold back dirt. When the fasteners fail, the wall fails. Standard deck screws have no place here. This part of the wood screw size chart covers structural timber screws and lag screw sizes for landscape work.

Structural Screws vs Lag Bolts for Retaining Walls

The old way was 3/8" x 12" galvanized spikes:

• Modern timber screws are faster and hold tighter. The Simpson SDWS (0.220" shank, T40 Torx drive) goes in with a regular drill and pulls the timbers together under compression. Spikes just pin them in place.
• Match screw length to timber size. 8" for 4x4 timbers, 10" for 6x6. The screw needs at least 2-3" of thread embedment depth into the bottom timber.
• For the base course, pound 1/2" rebar stakes (24 to 36 inches long) through the first timber every 4 feet. Nothing holds that bottom row to the ground like rebar. Railroad ties are a whole other story.
• Railroad ties are different. Dense hardwood soaked in creosote. They'll eat normal screw tips for breakfast. Use 1/2" rebar through pre-drilled 3/8" holes.
• Walls over 4 feet need an engineer. That's per IBC Section 105.2.

For light-duty landscape edging, Eagle Claw #12 x 4" 305 SS construction screws ($55.20/100-pack) handle 4x4 and 4x6 timber joints without rust stains.

Sauna, Hot Tub & Pool Deck Screw Sizes

These three share the same problem: heat, moisture, and chemicals beating on your screws nonstop. If there's one place to spend the extra money on 316 marine grade stainless, this is it.

Why These Projects Demand Stainless Steel Screws

Here's something people don't think about: a screw head in a sauna gets just as hot as the room. We're talking 180-200 degrees. Sit on an exposed screw head and you'll remember it for a while. That's why every bench screw has to go in from underneath, or get countersunk deep and plugged. Galvanized coatings break down in sustained heat. Only stainless steel fasteners survive inside a sauna.

• Hot tubs and pools are basically saltwater for your screws. The chlorine or bromine splashes onto the deck, evaporates, and leaves a concentrated salt film behind. Eagle Claw 304 SS starts pitting within a season or two next to a hot tub. Eagle Claw 316 SS handles it for decades.
• Don't mix metals around water. 316 SS screws with galvanized joist hangers on a hot tub deck creates a battery effect that corrodes the galvanized metal faster. Keep it all stainless.
• Pool fences have strict code. Min 48" high, max 4" picket gaps, self-closing gates. Use 316 SS because gate hardware takes constant stress.

More on the 304 vs 316 question in our stainless steel deck screws FAQ.

Treehouse, Playset & Outdoor Stair Screw Sizes

If kids are climbing on it, overbuild it. Smooth bolt heads, recessed hardware, and structural-grade fasteners at every load-bearing joint. No shortcuts.

Safety First: Screws for Load-Bearing Play Structures

I'll be straight with you: don't cut corners on treehouse and playset hardware. Your kids are climbing on it.

• Treehouses need specialty bolts, not regular screws. The pros use Treehouse Attachment Bolts (TABs) at 1-1/4" diameter. Each one holds 8,000-10,000 lbs. One big bolt does less damage to the tree than several small ones.
• Treehouse deck boards use the same screw sizing guide as a regular deck. Eagle Claw #10 x 2-1/2" 304 SS ($27.40/100-pack) for 5/4 boards. Countersink every head flush, and always two screws per joist.
• Playsets need carriage bolts, not screws. The smooth dome head means no cut fingers. All bolt ends recessed and capped with acorn nuts. The swing beam gets 1/2" carriage bolts because a swinging kid generates 2-3x body weight.
• Outdoor stairs? Countersink every tread screw. A protruding head on a stair is a trip waiting to happen. Add construction adhesive under the treads as backup.

What's the Difference Between #10 and #12 Screws?

Now that you've seen #10 and #12 pop up across all those wood screw size charts, here's what those screw gauge sizes actually mean. The #10 screw diameter is 0.190" (4.83mm). The #12 screw diameter is 0.216" (5.49mm). That makes the #12 about 14% thicker.

Both follow the same gauge formula: diameter = (gauge x 0.013) + 0.060 inches. The screw gauge system skips #11 entirely, jumping from #10 to #12. That 14% wood screw diameter increase gives you exactly 14% more withdrawal resistance because the holding power formula scales directly with diameter. Thread pitch also changes: 13 TPI for #10 vs 11 TPI for #12, giving the #12 deeper thread engagement.

Grab #10 for 95% of outdoor work. It's what Simpson Strong-Tie builds their entire Deck-Drive line around. Reach for #12 when you're going into thick or dense wood, or using screws longer than 4". Eagle Claw's #12 x 4" 305 SS construction screws ($55.20/100-pack) are built for that heavier work.

Is a #8 or #10 Screw Bigger?

A #10 is bigger. The #8 screw diameter is 0.164" (4.17mm). The #10 screw diameter is 0.190" (4.83mm). That's about 16% thicker, roughly the thickness of a credit card, but it's the line between "indoor screw" and "outdoor screw."

Think of #8 as the go-to for indoor projects. Cabinets, furniture, trim, shelving. #10 is the go-to for outdoor work: decking, fencing, garden beds, and anything built with 2x lumber. Wind, foot traffic, and rain put way more stress on an outdoor joint, and the thicker #10 shank gives you the extra shear strength and pullout resistance to handle it. That said, #8 is still the right size for thin fence pickets, light trim, and furniture slats where #10 would split the wood. The #6 screw diameter (0.138") drops even smaller for finish nailing and delicate interior hardware.

The Complete Wood Screw Size Chart by Project Type

This master wood screw size chart maps every outdoor project to the exact fastener size and brand you need.

Browse the full fastener catalog to find your exact size, or use the screw calculator to figure out how many you need.