What size tubular latch should I use?

The most common tubular latch sizes are 64mm (2.5 inches), 76mm (3 inches), 102mm (4 inches), 127mm (5 inches) and 152mm (6 inches). The correct size depends on your door thickness and whether you are fitting door handles or door knobs.

What is the backset on a tubular latch?

The backset is the distance from the edge of the latch faceplate to the centre of the spindle hole. It determines how far your door handle or door knob sits from the edge of the door.

Should I use a heavy duty tubular latch with door knobs?

Yes. Most traditional door knobs are unsprung, so a heavy duty double sprung tubular latch is recommended to ensure the knob returns correctly after use.

What size tubular latch is recommended for door knobs?

A 102mm (4 inch) tubular latch is generally recommended for door knobs, as it provides a greater backset and helps prevent your hand from catching the door frame. A 76mm (3 inch) latch can be used where space is limited.

Can I use a standard tubular latch with door handles?

Yes. Standard single sprung tubular latches are suitable for sprung door handles. Unsprung door knobs should always be paired with a heavy duty double sprung latch.

Choosing The Right Tubular Latch

How to Choose the Right Tubular Latch Size

A tubular latch is a simple, spring-assisted mechanical device used to keep a door closed without the need for a lock.

It is mortice fitted into the edge of the door, giving a flush finish rather than being surface mounted. Tubular latches are one of the most commonly used latch types in UK homes.

But how do you choose the correct type and size of tubular latch?

Heavy Duty, Double Sprung & Standard Tubular Latches

Heavy duty tubular latches are designed for doors with frequent or heavy use.

Double sprung latches have a heavier spring mechanism and are essential when fitting unsprung door knobs or unsprung door handles. This helps the knob or handle return to its original position without needing to be turned back manually.

Standard latches are single sprung and are not recommended for use with door knobs. These latches are best suited to sprung door handles.

Suffolk Latch Company heavy duty tubular latches are also double sprung, making them the recommended tubular latch for use with unsprung door knobs. Browse our range of basic, heavy duty and fire rated tubular latches.

Tubular & Mortice Latch Sizes

Tubular latch measurements and door latch sizes

The main tubular latch measurements to check are the overall case size and the backset.

Case Size/Depth

Tubular latches are available in a range of sizes, finishes and styles. The most common industry standard tubular latch sizes are:

64mm / 2.5 inches
76mm / 3 inches
102mm / 4 inches
127mm / 5 inches
152mm / 6 inches

Backset

The backset is the distance from the edge of the latch faceplate to the centre of the spindle hole. Each standard tubular latch size has a typical backset measurement, although there can be slight variation of around 1mm.

64mm / 2.5-inch case size = 45mm backset
76mm / 3-inch case size = 55mm backset
102mm / 4-inch case size = 80mm backset
127mm / 5-inch case size = 107mm backset
152mm / 6-inch case size = 130mm backset

Door Handles

Door handles are generally fitted with a standard 2.5-inch or 3-inch tubular latch.

Browse our door handles in a range of styles and finishes.

Door Knobs

To prevent hands and fingers catching on the side of the door frame, it is best to fit a door knob further from the edge of the door than a door handle.

The recommended case size for fitting with door knobs is 4 inches, although 3 inches can be used as an absolute minimum.

Most door knobs are unsprung, so a heavy duty, double sprung tubular latch is essential.

Browse our range of door knobs in rosewood, cast iron and bronze.

Comments

5 comments

Lawrence Dodge on Jan 14, 2025

Hello I am looking for a tubular latch and single deadbolt with a backset of 1 1/2" (38mm). Would you have anything like that? Thank you in advance Lawrence Dodge
Suffolk Latch Company on Jan 16, 2023

Hi Roy, Most latches have industry standard backset sizes, even those from different manufacturers. Some have rounded endplate designs rather than square. It sounds as if your latch might also be older and could have pre-metric measurements. All of our products have dimension drawings with measurements in mm. When replacing latches of a different size you will need to do a certain amount of filling and or additional morticing. Hope this helps.
ROY TUSTIN on Jan 16, 2023

I am replacing Legge latches and they appear to be different to standard latches. The latch has rounded ‘corners’ not square and the backset measurement is slightly different. The latches are 20 years old – does Legge use a different standard to other manufacturers?
Martin Keywood on Sep 27, 2022

Hello, I am fitting some round ceramic 60mm door knobs with ceramic rose back plate. They are not sprung. What size tubular latch would you suggest and do you supply them. Also what drill size is applicable to fit the latch. Many thanks Martin Keywood
Alan on Jan 12, 2022

Hi Do you sell barrel mortise latch heavy duty backset 75mm. Many thanks Alan