Flush Hinge Sizes: Butterfly and Offset Leaf Hinges in mm

Updated 2026-11-09 · RAYEN 雷茵

How does a flush hinge differ from a butt hinge?

On a butt hinge the two leaves are mirror images. Closed, they lie face to face, two leaves thick, so each usually sits in its own recess. On a flush hinge one leaf has a window cut in it, and the other leaf is shaped to fit that window. Closed, the inner leaf sits inside the outer one. Many fitters therefore screw them straight onto the door edge and frame without cutting a recess.

Check the gap your door needs on the drawing before you decide to fit without a recess.

Which shapes are there?

Our codes call these hinges centre pivot and offset pivot. In practice the names describe two shapes.

• Butterfly (centre pivot): the outer leaf has a shaped window, and the inner leaf is a matching decorative outline. 4x3x2.5-2BB Centre Pivot is 100 × 75mm, 2.5mm, Ø12.2mm, in stainless. 4x3x3.3-2BB has the same butterfly outline in brass, at 100 × 79mm, 3.3mm, Ø14.6mm.
• Rectangular (offset pivot): the outer leaf has a square window, and the inner leaf is a plain rectangle.

Which sizes come in the rectangular shape?

• 4x3x2.5-2BB Offset Pivot: 100 × 73mm, 2.5mm, Ø12.2mm.
• 4x3x3.0-2BB Offset Pivot: 100 × 75mm, 3mm, Ø14.2mm.
• 5x3x2.5-2BB Offset Pivot: 125 × 78mm, 2.5mm, Ø12.2mm.
• 5x3.5x3.0-2BB Offset Pivot: 125 × 82mm, 3mm, Ø14.2mm.

All are stainless 304/201 in Satin Sanded, with two ball bearings. The brass butterfly hinge is in Frosted Copper.

Why are the sizes metric?

The codes read like inch codes, 4x3 and 5x3.5, but these hinges are made to round metric sizes: 100mm and 125mm high, not 101.6mm and 127mm. A 4x3 flush hinge is therefore 1.6mm shorter than a 4x3 butt hinge in stainless. If you are swapping a butt hinge for a flush one, or the other way round, measure. The inch to mm guide lists the other metric codes.

How do they compare with the rest?

Flush hinges sit in the 100mm and 125mm rows. Every one of them has two bearings. For a heavy or busy door, compare them with the 4BB butt hinges in the same rows. See how many ball bearings.

What should you measure when replacing one?

• Leaf height and the open width across both leaves.
• The shape: butterfly outline or plain rectangle. Take a photo of the hinge opened flat.
• Leaf thickness and knuckle diameter.
• Screw-hole positions against the old holes in the door and frame.

A worked example

A furniture maker replaces hinges on interior doors fitted with stainless flush hinges. The old hinge opens to 125mm by 82mm, with a square window and a 3mm leaf. That is 5x3.5x3.0-2BB Offset Pivot. If it measured 125 × 78mm with a 2.5mm leaf, it would be 5x3x2.5-2BB Offset Pivot. Both look alike from a metre away, which is why the caliper reading matters.

If the same maker wants a brass look on a new line, 4x3x3.3-2BB is the butterfly shape in brass. It is 100 × 79mm, so it is not a drop-in for the 100 × 75mm stainless butterfly hinge.

How heavy a door can they carry?

No load figure is printed for flush hinges, or for the butt hinges in the same rows. If the door is heavier than a normal room door, or a closer pulls on it, send us the weight and height, and we confirm the hinge and how many to fit.

What is the next step?

Send a photo of the old hinge laid open beside a ruler, with your measurements, to [email protected], and we name the model and send its drawing. For a quick identification, send the same photo to the factory owner on WhatsApp. The number is on the contact page. The hinge size converter turns a code into millimetres.

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