Ball Bearing Hinge Size Chart: Measured Sizes in mm, Not Just Codes

Updated 2026-11-05 · RAYEN 雷茵

How do you read a hinge code?

Take 4x3x3.0-4BB. The first figure is the height in inches, the second is the width across both open leaves, and the third is the leaf thickness in mm. The last part is the bearings: 4BB means four ball bearings.

A word after the code tells you the type. US standard, rounded corner, offset pivot, centre pivot, and single-pin or twin-pin security each appear in the chart below.

What should you measure?

If you are matching an old hinge or a routed door, take these with a caliper.

• Height of the leaf.
• Width across both leaves when open flat.
• Leaf thickness.
• Knuckle diameter.
• Screw-hole layout. Lay the old hinge on the drawing.
• Material. A magnet will not settle it, so ask for the grade.

Ball bearing hinge size chart

Leaf size is height × open width. The chart sorts by height. Where one code appears twice, the Material column tells the two apart.

5x3.5x3.5-1BB and 8x4x3.5-4BB Single Security Stud are not in the chart. Ask us for their measured sizes.

Why does the same code give two sizes?

Our stainless hinges mostly follow inch sizes. Several brass hinges and the pivot types are made to metric sizes. The code stays the same, and the part does not.

• 4x3x3.0-4BB in stainless: 101.6 × 76.2mm, Ø14.2mm. 4x3x3.0-4BB in brass: 100 × 75mm, Ø12mm.
• 5x3x3.0-4BB in stainless: 127 × 76.2mm, Ø14.2mm. 5x3x3.0-4BB in brass: 125 × 75mm, Ø12mm.
• 4x3x2.5-2BB Offset Pivot offset pivot: 100 × 73mm. 5x3.5x3.0-2BB Offset Pivot offset pivot: 125 × 82mm.
• 4x3x3.0-0BB in brass: 100 × 70mm, Ø10mm. 4x3x3.3-2BB in brass: 100 × 79mm, Ø14.6mm.

A 1.6mm change in height is enough to stop a leaf dropping into a door routed for the other hinge. Take the size from the row with the right material.

What is different about US standard hinges?

4x3x3.0-4BB US and 4x3x3.0-4BB read the same in the chart: 101.6 × 76.2mm, 3mm, Ø14.2mm, four bearings. The difference is on the drawing. The screw holes sit in another pattern, so a door or frame prepared for one will not line up with the other. If your door has a template, send it with the enquiry.

What sizes do security hinges come in?

The twin-pin models are 4x4x3.0-4BB Double Security Stud and 5x4x3.0-4BB Double Security Stud. The single-pin stainless model is 6x4x3.5-4BB Single Security Stud. Their drawings show studs on the leaf and matching holes opposite, so the door and frame stay engaged when closed. Read the leaf size in the chart, and take the stud positions from the drawing.

A worked example

You are replacing hinges on a door routed for a brass hinge. The old leaf measures 100 × 75mm, 3mm thick, with a Ø12mm knuckle. That is 4x3x3.0-4BB in brass. If the door should now take stainless, the same code gives you 101.6 × 76.2mm, so the routing must grow. 4x3x3.0-2BB Offset Pivot is 100 × 75mm in stainless, but it is an offset pivot hinge with a different leaf shape, so it is no direct swap. Send us a photo with the measurements and we match it.

What should you write on the order?

• Full code, with the word after it: US standard, rounded corner, offset pivot.
• Material. For stainless, state 304 or 201.
• Leaf size in mm, copied from the chart, as a check against the code.
• Finish, such as Satin Sanded for stainless or Frosted Copper for brass.
• Quantity.

Writing the millimetre size beside the code costs one line, and it catches the wrong hinge before it ships.

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