A furniture screw is specified by three numbers, and misreading any one of them sends the wrong screw into the wrong hole. The diameter decides the holding strength, the length decides the grip, and the thread decides how the screw bites the material — and the sizes come in two systems, metric millimetres and imperial gauges, that overlap and confuse. This guide is the reference: the standard furniture screw sizes, how to read them, and how to choose the right screw for the joint. Based on 15 years of manufacturing furniture fasteners across 40+ countries.
How Screw Sizes Are Written
Metric Millimetres and Imperial Gauges
The first step is reading the size correctly, because the same screw can be described two ways.
| System | Diameter | Length | Example |
| Metric | Millimetres (M4, M5) | Millimetres (20, 40) | M5 × 40 |
| Imperial | Gauge (#6, #8, #10) | Inches or mm (1", 32mm) | #8 × 1¼" |
Metric measures the thread diameter. An M5 screw has a 5mm thread diameter, and the length follows — M5 × 40 is 5mm in diameter and 40mm long. It is the system used across furniture manufacturing and most of the world.
Imperial measures in gauge. A #8 screw is 8 gauge, a number that maps to a diameter (roughly 4.2mm for #8). The gauge is a historical scale, not a direct measurement, which is why a chart is needed to translate it.
The two systems overlap. A #8 and an M4 are close in size, and a #10 and an M5 are close too. The screw is the same physical thing; only the name changes. Reading both is the price of sourcing across markets.
Furniture screws in metric and imperial
The Diameter Chart
The Gauge and the Millimetre
| Gauge | Approx. Diameter | Metric Equivalent | Typical Furniture Use |
| #4 | 2.8mm | M3 | Hinges, catches, light hardware |
| #6 | 3.5mm | M3.5 | Drawer slides, light panels |
| #8 | 4.2mm | M4 | General furniture assembly |
| #10 | 4.8mm | M5 | Heavier joints, legs, rails |
| #12 | 5.5mm | M6 | Heavy structural joints |
The diameter sets the holding strength. A screw's grip in the material grows with its diameter, because more thread is in contact with more material. A #8 is the general furniture workhorse; a #10 or #12 is for joints that carry real load, like legs and rails.
The diameter also sets the split risk. A large screw needs more material around it, and driven too near a panel edge it splits the board. The diameter must match both the load and the available material — a #12 in a thin edge is a split waiting to happen.
Choose the diameter for the load, then check the material. The load decides the strength needed, and the material decides whether that diameter can be driven without splitting. The two together settle the screw.
The Length Chart
How Long Is Enough
| Screw Length | What It Does | Typical Use |
| 12-16mm | Thin panels, shallow joints | Hardware mounting |
| 20-25mm | Standard panel joints | Cabinet assembly |
| 30-40mm | Deeper grip, thicker panels | Legs, rails, framing |
| 50mm+ | Maximum grip, thick stock | Heavy structural joints |
The length sets the grip depth. A screw holds by the thread buried in the material, and the more thread in the material, the stronger the hold. The rule of thumb: the screw should penetrate about two-thirds of the receiving material's thickness.
Too short strips, too long breaks through. A screw that barely enters the receiving panel has little thread to grip and pulls out under load. A screw that penetrates too far pokes through the far face, and that is a finish defect. The length is chosen to sit between the two.
Measure the joint, not the habit. The correct length is the receiving material's thickness, times about two-thirds, plus the thickness of the panel being fastened. A chart is a starting point; the joint is the answer.
Furniture screws in every length
The Thread Types
The Thread Decides the Bite
| Thread Type | What It Is | Best For |
| Machine thread | Fine, uniform thread | Metal, inserts, nuts |
| Wood thread | Coarse, self-tapping | Solid wood |
| Chipboard / particle board | Deep, wide thread | Particleboard, MDF |
| Twin / double thread | Two leads, faster grip | Production, soft board |
| Self-tapping | Cuts its own thread | Thin metal, plastic |
The thread matches the material. A wood thread bites the grain of solid wood; a chipboard thread cuts into the composite core of particleboard; a machine thread screws into a nut or an insert. The thread type and the material are one decision, not two.
The chipboard thread is the furniture standard. Because modern furniture is largely particleboard and MDF, the deep, wide chipboard thread is the workhorse — it cuts into the soft core and holds where a wood thread would strip out.
The twin thread is for production. Two thread leads cut into soft board twice as fast and grip with more surface area, which is why power-driven production lines favour it. It is the chipboard thread, optimized for speed.
The Head Types
How the Screw Is Driven and Finished
| Head Type | Drive | Characteristics | Best For |
| Countersunk (CSK) | Pozi / Phillips | Flush finish | General furniture |
| Pan head | Pozi / Phillips | Rounded, visible | Hardware, brackets |
| Raised / oval | Pozi / Phillips | Decorative | Visible, traditional |
| Hex head | Hex key | High torque | Structural, workshop |
| Torx | Torx driver | No cam-out | Production, high torque |
The countersunk head is the furniture default. It seats flush with the surface, giving the clean, hidden finish that furniture expects. The drive recess — Pozi is preferred over Phillips in Europe — decides how well the driver grips without slipping.
The Torx head is the production choice. A Torx drive does not cam out under high torque, so it can be driven hard and fast without stripping — the reason production lines moved to it. It is the head for consistent, power-driven assembly.
The head follows the look and the torque. A visible screw in a visible place takes a pan or raised head for the look; a high-torque structural joint takes a hex or Torx for the drive. The head is chosen for how the screw is driven and how it should look.
Screws for every head and drive
Reading a Screw Spec
Putting the Three Numbers Together
| Spec Element | What It Names | In an Example |
| Diameter | The strength | M5 (or #10) |
| Length | The grip | 40mm (or 1½") |
| Thread | The material match | Chipboard / wood |
| Head | The drive and finish | Countersunk, Pozi |
A full spec reads as one string. "M5 × 40 chipboard, countersunk Pozi" names a screw that is 5mm in diameter, 40mm long, with a particleboard thread and a countersunk Pozi head — every fact needed to buy the right screw, in one line.
The three numbers answer three questions. The diameter answers "how strong," the length answers "how deep," and the thread answers "into what material." Miss any one, and the screw is wrong for the joint.
The chart is a map, the joint is the destination. This guide gives the standard sizes and what they mean; the specific joint — its load, its material, its thickness — is what picks the actual screw. Read the chart to understand the screw, then match it to the joint.
The complete furniture screw range
Common Mistakes
The Errors That Put the Wrong Screw In
| Mistake | Consequence | The Fix |
| Confusing gauge and millimetre | Wrong diameter | Use the conversion chart |
| Screw too short | Inadequate grip | Penetrate two-thirds of the material |
| Wood thread in particleboard | Strips out | Use a chipboard thread |
| Screw too large for the edge | Split panel | Match diameter to the material |
| Wrong head for the drive | Stripped recess | Match the head to the driver |
The unifying lesson: a furniture screw is specified by three numbers and a material match, and each has its own error. Read the diameter, choose the length for the grip, and match the thread to the material — then the screw holds, the joint stays tight, and the furniture does what it was built to do.
Conclusion
The furniture screw size chart is the map that turns a confusing mix of gauges, millimetres, lengths, and threads into a clear decision. The diameter sets the strength, the length sets the grip, the thread sets the material match, and the head sets the drive and the finish. Read all four, and match them to the joint — the load, the thickness, and the material — and the right screw goes into the right hole, and the joint holds for the life of the furniture.
Key takeaways:
At Shaxi Hardware, every furniture screw ships with documented diameter, length, thread type, and head specification, matched to the panel material and the joint. Our ISO 9001 certified facility batch-tests every production run, and our technical team helps spec the screw for any furniture joint. Because the right screw is the one that matches the joint — and we make the match easy.
Request a furniture screw size chart
Additional Resources
- [Link to: /collections/chipboard-screw – Furniture / Chipboard Screws]
- [Link to: /collections/confirmat-screw – Confirmat Screws for Panel Joints]
- [Link to: /collections/insert-nut-sockets – Threaded Inserts & Nuts]
- [Link to: /collections/connecting-fittings – Furniture Connectors]
- [Link to: /pages/about-us – ISO 9001 Manufacturing & Testing]
- [Link to: /pages/contact – Selection Consultation]
About Shaxi Hardware
With over 15 years of experience manufacturing furniture fasteners, Shaxi Hardware serves brands and manufacturers across 40+ countries. Our ISO 9001 certified production facility manufactures furniture screws of every diameter, length, thread type, and head, with documented specifications matched to the panel and the joint. Batch quality control is conducted on every production run, and our technical team supports screw specification for any furniture application. Third-party verification by SGS, TÜV, Intertek, or Bureau Veritas is welcomed.
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