# Door advice: measuring, sizes, trimming and fitting > Straight answers on measuring a door opening, UK door sizes, trimming allowances, frames and linings, finishes and safety glass. Source: https://example.co.uk/advice --- # Everything worth knowing before you order a door Doors go wrong on four things: the size, the thickness, how much can be trimmed off, and the parts nobody mentions until the leaf arrives on its own. These guides deal with all of them, in plain English, with the measurements you actually need. ## What do I need to know before buying an internal door? Four things: the size of the door or the opening, whether the lining is staying, the thickness, and how much the door can be trimmed. Get those right and the rest — style, finish, ironmongery — is preference rather than a return. ## Getting the size right Almost every door that has to go back was the wrong size. These three cover measuring, the UK size families, and how much a door can safely be cut down. - [AI illustrationHow to measure a door opening9 questions answeredHow do I measure for a new internal door?](https://example.co.uk/advice/how-to-measure-a-door) - [AI illustrationUK door sizes explained: imperial and metric11 questions answeredWhat size are UK internal doors?](https://example.co.uk/advice/door-sizes) - [AI illustrationHow much can you trim off a door?8 questions answeredHow much can you trim off a door?](https://example.co.uk/advice/how-much-can-you-trim-a-door) ## Glass and the regulations Where the safety-glass rules sit and what they mean for a glazed door. Orientation only — building control has the final word on your project. - [AI illustrationGlazed doors and safety glass11 questions answeredDoes a glazed internal door need safety glass?](https://example.co.uk/advice/glazed-doors-and-safety-glass) ## Fitting and finishing Frames and linings, everything a door needs besides the leaf, and how to finish one so it stays flat. - [AI illustrationDoor frames, linings and casings: the difference10 questions answeredWhat is the difference between a door frame, a door lining and a door casing?](https://example.co.uk/advice/door-frames-linings-and-casings) - [AI illustrationHanging a door: hinges, latches and what a doorset includes11 questions answeredWhat do I need to hang an internal door?](https://example.co.uk/advice/hanging-a-door) - [AI illustrationUnfinished, primed or pre-finished doors11 questions answeredWhat is the difference between an unfinished, primed and pre-finished door?](https://example.co.uk/advice/door-finishes) ## The questions we get asked most ### What do I need to know before buying an internal door? Four things: the size of the door or the opening, whether the lining is staying, the thickness, and how much the door can be trimmed. Get those right and the rest — style, finish, ironmongery — is preference rather than a return. ### What is the most common internal door size in the UK? 1981 x 762 x 35mm, known as a 78 x 30 because it is 78 inches by 30 inches converted to millimetres. It is the standard room-door size across most of the existing UK housing stock. ### Do doors come with hinges and handles? Usually not. A door leaf is normally sold on its own, with hinges, latch, strike plate and handles bought separately. A doorset is the exception: it arrives with the frame or lining, hinges and latch already fitted. ## Using an assistant to shop? We publish a plain-text knowledge file at [/llms.txt](https://example.co.uk/llms.txt) covering the UK standard size tables, the safety-glass rule, the trimming rule and links to every guide here. It is written to be quoted accurately rather than to sell anything, and our robots.txt welcomes AI crawlers.