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64mm or 76mm door latch: case length is not the backset

Updated: October 2026

You are looking at two packets, one marked 64 mm and one marked 76 mm, and the door will only accept one of them. A 64mm or 76mm door latch choice is a choice of case length. The backset is a second measurement, and UK listings sometimes swap the words. This page is why the Yale title can say 64 mm backset while Yale's fitting sheet says 45 mm. Prices are on the [door fitting comparison](/hub/door-and-window-security/door-fitting). Peter F. used UK measuring guides and those listings in October 2026. A qualifying purchase through an amazon.co.uk link can earn a commission at no extra cost to you.

You are looking at two packets, one marked 64 mm and one marked 76 mm, and the door will only accept one of them. A 64mm or 76mm door latch choice is a choice of case length.

Our top picks

MOXYOY MOXYOY 45 mm tubular latch

Best overall

MOXYOY MOXYOY 45 mm tubular latch
8.0/10about £5.49
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Yale Yale PM888 tubular mortice latch

Rank 2

Yale Yale PM888 tubular mortice latch
8.8/10about £5.99
View offer
Chliinl Chliinl 45 mm tubular latch

Rank 3

Chliinl Chliinl 45 mm tubular latch
7.6/10about £5.29
View offer
On this page
  1. 1.Two different measurements
  2. 2.The 64 mm case
  3. 3.The 76 mm case
  4. 4.If the listing and the latch disagree

Two different measurements

Case length is how far the round body reaches into the door. On a UK internal door the two common lengths are 64 mm, which is 2½ inches, and 76 mm, which is 3 inches. Backset is the distance from the faceplate to the centre of the spindle. A longer case lets the handle sit further from the edge. The backset is the figure your existing handle hole has already fixed. Buy 64 mm when the handle centre is about 45 mm from the edge, and 76 mm when it is about 57 mm. Move to the other size only when you are prepared to drill a new spindle hole. Spring and door type stay on the tubular mortice latch buying guide.

The 64 mm case

A 64 mm case is the short tubular latch, and the backset UK retailers pair with it is about 44–45 mm. Yale's UK fitting sheet says: for a 64 mm latch, drill the spindle hole 45 mm from the edge. The short case is also the one More Handles points to for a glazed door, because the body reaches less far towards the glass. The Yale listing says the mortice latch has a 2.5 inch / 64 mm backset. Treat 64 mm on that packet as the case length unless your tape says otherwise. Which pack to open once you have measured is on the best tubular latch page.
MOXYOY MOXYOY 45 mm tubular latch

Testsieger

MOXYOY MOXYOY 45 mm tubular latch
8.0/10about £5.49
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The 76 mm case

A 76 mm case is the longer body, and the backset UK guides pair with it is about 56–57 mm. More Handles uses 56 mm. Yale's fitting sheet uses 57 mm from the edge. The extra length keeps your knuckles off the architrave. You do not gain that clearance by pushing a 76 mm latch into a door whose handle is already at 45 mm. The follower will sit about 12 mm further in than the old spindle hole. Choose 76 mm when you are hanging a new door or the old latch was already the long case. The longer case also needs a deeper edge hole. Those depths are on how to fit a tubular latch.

If the listing and the latch disagree

MOXYOY calls its figure a 45 mm edge distance. Chliinl calls its figure a 45 mm margin. Neither states a case length. A stated 45 mm usually belongs with a 64 mm case. It is not proof the body is 64 mm long. Lay the new latch next to the old one. If the round bodies differ by about 12 mm, you have mixed the two cases. One verified MOXYOY review measured 43 mm, not the 45 mm printed and stamped. If the goods do not match the description, the Consumer Rights Act 2015 short-term right to reject normally runs for 30 days. A title that calls 64 mm the backset is a wording problem you can resolve with the fitting sheet and a tape, when the body still matches the door.

Common questions

Why does the Yale title say 64 mm backset?
The amazon.co.uk listing for the PM888 three-pack says the latch has a 2.5 inch / 64 mm backset. Yale's UK fitting sheet, for a 64 mm latch, tells you to place the spindle 45 mm from the edge. Both sentences are in the sources. Use the sheet and your tape for the hole, and treat 64 mm on that listing as the case length unless the door itself measures otherwise.
Can I swap a 64 mm latch for a 76 mm one?
Only if you drill a new spindle hole about 12 mm further in and accept the old hole. The existing handle position will not meet the new follower. Most internal doors should keep the case they already have. A glazed stile is a reason not to move to the longer case at all.
What if I measure 43 mm?
A reading of 43 mm is shorter than the usual 45 mm backset on a 64 mm case. One MOXYOY review measured 43 mm against a stated 45 mm, and the handles would not line up. Compare the new latch with the old one before you enlarge the door. If the goods do not match the stated size, you can reject them under the Consumer Rights Act 2015, normally within 30 days.
Which size suits a glazed door?
The shorter 64 mm case is the one More Handles points to when the stile is glazed, because the body reaches less far towards the glass. Stay on 64 mm if that is what the door already has. Do not fit a 76 mm case into a narrow glazed stile to gain knuckle room. If the glass or the bead is already cracked around the old hole, stop.
Do the 45 mm listings match a 64 mm case?
A stated 45 mm edge distance is the backset that usually belongs with a 64 mm case. MOXYOY and Chliinl state 45 mm and do not state the case length, so check the body against the old latch. Yale's sheet does pair 45 mm from the edge with a 64 mm latch, which is the pair to trust over the listing's 64 mm backset line.

Related pages

Internal door latch

Door fitting

Best tubular latch UK: three listings for three jobs

Tubular mortice latch: what to measure before buying

How to fit a tubular latch on an ordinary internal door

Sources

Public UK and manufacturer sources from the research digest. Prices, stars and review counts are the amazon.co.uk figures in this comparison, not a live check on 21 October 2026. None of these listings was treated as BS 3621 or fire-door ironmongery.

  1. ERA 189-33 tubular mortice latch fitting instructions (retrieved 21 October 2026)
  2. Yale tubular latch fitting instructions (retrieved 21 October 2026)
  3. More Handles tubular latch guide (retrieved 21 October 2026)
  4. Home Secure internal door latch measuring guide (retrieved 21 October 2026)
  5. GAI specifiers' guide: ironmongery and security, September 2024 (retrieved 21 October 2026)
  6. GOV.UK fire safety (England) regulations 2022: fire door guidance (retrieved 21 October 2026)
  7. Approved Document B: fire safety frequently asked questions (retrieved 21 October 2026)
  8. Consumer Rights Act 2015, sections 11 and 22 (retrieved 21 October 2026)