US Standard Hinges: Sizes, Screw Holes and How They Differ

Updated 2026-11-08 · RAYEN 雷茵

What does US standard mean on a hinge code?

US standard is the factory's name for this hinge pattern, written in Chinese after the code. It is a name for the pattern, not a certificate, so if your project names a standard, send us the clause and we compare it with the drawing.

What the drawings do show is a consistent difference in the screw holes. Compare 4x4x3.0-4BB US with 4x4x3.0-4BB. Both are 101.6 × 101.6mm, 3mm thick, with a Ø14.2mm knuckle and four ball bearings. The plain hinge has its four holes per leaf in a zigzag, alternating near and far from the knuckle. The US standard hinge has four holes per leaf placed symmetrically, so the top half mirrors the bottom half. 4x3.5x3.0-4BB US against 4x3.5x3.0-4BB, and 4x3x3.0-4BB US against 4x3x3.0-4BB, show the same thing.

Which US standard hinges are there?

All are stainless steel, listed as 304/201, in Satin Sanded.

• 4x3x3.0-2BB US and 4x3x3.0-4BB US: 101.6 × 76.2mm, 3mm, Ø14.2mm.
• 4x3.5x3.0-2BB US and 4x3.5x3.0-4BB US: 101.6 × 89mm, 3mm, Ø14.2mm.
• 4x4x3.0-2BB US and 4x4x3.0-4BB US: 101.6 × 101.6mm, 3mm, Ø14.2mm.
• 4.5x4x3.0-2BB US: 114.3 × 101.6mm, 3mm, Ø14.2mm.
• 4.5x4x3.5-2BB US: 114.3 × 101.6mm, 3.5mm, Ø15.2mm.
• 4.5x4.5x3.5-2BB US: 114.3 × 114.3mm, 3.5mm, Ø15.2mm.

Up to 4 inches you can choose two or four bearings on the same leaf. The 4.5-inch sizes come with two bearings. Leaf thickness and knuckle grow together. The 3.5mm leaves carry the Ø15.2mm knuckle.

How do they compare with the rest of the range?

This chart lists every ball bearing hinge by height. The US standard hinges sit among them at 101.6mm and 114.3mm. No other hinge in the range is 114.3mm high, so a 4.5-inch hinge is a US standard hinge.

What should you measure before ordering?

• Leaf height and open width, with a caliper.
• Leaf thickness and knuckle diameter.
• Screw-hole positions. Lay the old hinge or the door template on our drawing.
• Corner shape. These hinges have square corners. For round corners, see rounded or square corner hinges.

Two worked examples

Doors arriving pre-drilled

A door factory sends doors and frames already prepared for 4 × 4in hinges with a symmetrical hole pattern. Order 4x4x3.0-4BB US. The plain 4x4x3.0-4BB has the same leaf, but its zigzag holes will miss the pilot holes.

A taller, heavier door

A project wants a 4.5 × 4.5in hinge in 3.5mm stainless. That is 4.5x4.5x3.5-2BB US: 114.3 × 114.3mm, Ø15.2mm knuckle, two ball bearings. If the door also needs four bearings, tell us. That size is listed with two, and we confirm anything else against a drawing first.

Why does the hole pattern matter so much?

A screw that misses its pilot hole by a few millimetres wanders, splits the timber, or strips in a thin metal frame. On a run of pre-drilled doors, the fitter then drills new holes by hand, door after door. Matching the pattern before you order costs one drawing. Getting it wrong costs labour on every door in the job.

Two or four bearings?

Up to 4 inches, each US standard size comes as 2BB and 4BB on the same leaf, so you can choose by the door without changing the recess. Start from four bearings on a heavy or busy door. The ball bearing guide explains where the bearings sit.

What should you write on the order?

• Full code with US standard written after it.
• Leaf size in mm, thickness and knuckle diameter.
• Stainless grade: 304 or 201.
• Finish: Satin Sanded.
• Quantity, and the door template if you have one.

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