​Understanding Bolt Sizes for Sofa or Lounge

It can be hard to determine which bolt size your sofa or lounge uses if you want to change or replace your sofa legs. This guide will look at the common sizes and provide some tips to identify the bolt size you need:

5/16" Bolts

Diameter: 5/16 inches (7.94 mm)

These are by far the most common bolt size used on sofa legs. Particularly with sofas imported for the Australian market. Why an imperial size? This is the standard required by the American market that most of the sofas are made for.

M8 Bolts

Diameter: 8 mm

Frequently used in European imported sofas and IKEA sofas. Not all IKEA sofas use M8 bolts (Metric 8mm) as they can have varied ways of attaching the legs, but most that have a central bolt on the leg do.

3/8" Bolts

Diameter: 3/8 inches (9.53 mm)

These are more heavy-duty bolts and can often be found in larger imported sofas.

M10 Bolts

Diameter: 10 mm

These Metric 10mm bolts are the heavy-duty version of M8 used on European imported sofas.

Identifying which bolt I have:

The easiest way to measure the diameter of the bolt. Remember to measure the whole thread from tip to tip

The metric bolts will be precisely 8mm or 10mm and the Imperial bolts will be slightly under at 7.94 and 9.53, a pair of calipers can help here if you have them.

Due to how close in size the M8 and 5/16” bolts are, you may think they are interchangeable. However, they have a different thread pitch (how steep the thread is), so after a few turns, they will go out of alignment and lock up. You can use this behaviour to help identify the type of thread if you have an M8 or 5/16” nut. Hardware stores such as Bunnings will often have a thread-size testing board for just such a purpose.

Selecting the right leg

Urban Hardware works with a range of suppliers, from larger suppliers who only use 5/16” bolts to small batch suppliers who can customise the sofa leg to use a specific bolt. Have a look through the Urban Hardware Range to find a leg that meets your requirements.

If you have selected a leg that can’t be customised and is not the right bolt size for your sofa, you can use the Urban Hardware Mounting Plates, T-nuts, or Inserts to mount it to your sofa.

Hope this article has been helpful in your buying process!