Door Hanging Calculator

The standard UK convention is 150mm (6 in) from the top of the door to the top of the upper hinge, and 225mm (9 in) from the bottom of the door to the bottom of the lower hinge. A third (centre) hinge, where used, goes midway between the two. Fire doors and most external doors must have at least 3 hinges. Some carpenters set the top hinge at 225mm instead — either is workable, but 150mm/225mm is the common rule of thumb.

The standard latch (handle) height is 990-1050mm from the finished floor to the centre of the latch. Most handles are set at 1000mm. For accessibility (Part M), handles should be 900-1050mm high and operable with one hand. Lock/deadbolt mechanisms are typically fitted above or below the handle.

Standard margins are 2-3mm on the hinge side, 2-3mm on the latch side, and 2-3mm at the top. The bottom gap should be 8-10mm for carpet clearance (or 3-5mm for hard floors). Fire doors require a maximum 3mm gap at the top and sides (with intumescent strip) and a maximum 8mm gap at the bottom (or 3mm with threshold seal). For lining and architrave quantities, see our Door Lining Calculator.

FD30/FD60 fire doors require: at least 3 fire-rated hinges (CE or UKCA marked, e.g. to EN 1935), an intumescent strip to the head and both jambs (3 sides — the threshold is not strip-sealed), a cold smoke seal where smoke control is needed, a self-closing device (overhead or concealed closer), a fire-rated lock/latch, and no letter plates unless fire-rated. FD30 doors generally use a 10–15mm seal; FD60 doors typically need a 20mm seal (or twin strips) and heavier-grade hardware. All hardware must be CE or UKCA marked and suitable for the specific certified doorset.

Standard internal doors need 2 hinges (75mm or 100mm butt hinges). Doors over 2040mm tall and all fire doors need at least 3 hinges. External doors almost always need 3 hinges because of their weight, and very heavy or thick leaves (typically over about 40kg, or escape-route doors) may take 4 hinges. The third hinge prevents the door from warping and distributes the weight more evenly. This calculator returns 3 hinges for fire and external doors automatically.