How to measure for a new door (and which size to order)
Doors come in two standard heights, 2040mm and 2340mm. Internal doors are 35mm thick, entrance doors are 40mm thick, and the standard entrance door is 2040 x 820 x 40mm. To choose a size, measure the opening, allow 3mm clearance at each side and the top plus your floor clearance, then pick a standard door you can reach by trimming no more than 3mm from any edge.
Key takeaways
- Door width = opening width minus 6mm. Door height = opening height minus 3mm minus floor clearance.
- The manufacturer allows a maximum of 3mm to be trimmed from any edge, done evenly. BAL40 doors cannot be trimmed.
- Solid and entrance doors up to 2040 x 820mm need three hinges. Larger doors need four or a pivot system.
- If your numbers do not land on a standard size, you need a made to order size.
What size is a standard internal door?
Internal doors are 35mm thick and made in 2040mm and 2340mm heights. Depending on the range, standard widths are 410, 420, 460, 520, 620, 720, 770, 820, 870 and 920mm.
Width matters in new homes. The manufacturer's NCC 2022 guide explains that the Livable Housing requirements call for an 820mm minimum clear opening at selected doorways, and that a hinged door 870mm wide or wider provides it.
What size is a standard front door?
The standard entrance door is 2040 x 820 x 40mm. Many entrance ranges also offer 870, 920, 1020 and 1200mm widths and a 2340mm height as made to order size options. Some designs are 1200mm wide as standard: the Savoy 1200 range, Illusion XIL21 and XIL26, and Nexus NEX40.
| Door type | Heights (mm) | Widths (mm) | Thickness |
|---|---|---|---|
| Internal hinged doors | 2040, 2340 | 410 to 920, by range | 35mm |
| Entrance doors | 2040 (2340 option) | 820 standard; 870, 920, 1020, 1200 options | 40mm |
| Entrance sidelites | 2040 | 400 (200 in Newington) | 40mm |
| BAL40 bushfire doors | 2040 (2340 option) | 820 standard; 870, 920, 1200 options | 45mm |
How do I measure for a replacement door?
Measure the opening in the existing jamb rather than copying the old door, which may have been trimmed. The manufacturer's installation steps are:
- Measure the width of the opening at the top, middle and bottom.
- Measure the height on both the left and right side of the jamb.
- Door width = opening width minus 6mm (3mm clearance each side).
- Door height = opening height minus 3mm at the top, minus the floor clearance, which varies with your floor covering.
- Choose a standard size no more than 6mm larger than your result in each direction, because only 3mm can come off each edge.
Example: an opening 822mm wide gives a door width of 816mm, so an 820mm door trimmed 2mm per side works. An opening 805mm wide gives 799mm, which would mean taking 21mm off an 820mm door, so it needs a made to order size.
How much can you trim off a door?
The manufacturer's guarantee allows a maximum of 3mm to be trimmed from any edge, done evenly. The price list puts it as 3mm from the top, the bottom and each stile, so at most 6mm off the width and 6mm off the height. Cutting or fitting hardware must not weaken the door, and BAL40 bushfire doors cannot be trimmed at all. The bottom of a door carries the date of manufacture, which helps you mark it the right way up. Seal trimmed edges before hanging, as covered in painting, sealing and caring for timber doors.
How many hinges does a door need?
- Internal hollow core doors: two hinges. Prehung supplies 2340mm high hollow core doors with three.
- Entrance and solid doors up to 2040 x 820mm: three hinges.
- Larger entrance and solid doors: at least four hinges or a pivot system.
- BAL40 doors: at least four 100mm butt hinges.
The manufacturer's hinge guide places the top hinge at least 150mm from the top of the door, and the lowest hinge 230mm from the bottom.
When do you need a custom size?
You need a made to order size when your calculated door is more than 6mm under the nearest standard size, or larger than any standard size. Many entrance ranges can be made from 1990 x 805 x 40mm up to 2400 x 1200 x 40mm, and internal ranges such as Hampton from 1990 x 400 x 35mm up to 2400 x 1200 x 35mm. Limits vary by range, and some, such as Frontier Ultimate barn doors, are not offered in special sizes. For odd openings, Blockboard (STPC) flush doors are designed to be cut to size.
Cancellations or alterations to made to order doors are only accepted on the day of ordering, so check your measurements twice. Doors over 2400mm high or 1020mm wide are not guaranteed against warp.
What about the jamb or frame?
For a new internal opening, the Prehung system supplies the door already hinged to a knock down jamb. 2100mm high jambs suit 2040mm doors, 2400mm jambs suit 2340mm doors, and jamb widths are 92, 98, 112 and 116mm. Order the door and jamb together.
A Weatherguard entrance frame for a single 2040 x 820mm door has a unit size of 2110 x 887mm (plus or minus 5mm), in a 140mm or 160mm frame depth. Wider and 2340mm high doors need a frame upgrade. For pairs, rebating reduces the overall width by 12mm, while a mushroom stop adds 12mm.
Measuring checklist
- Location: internal, entrance or bushfire zone (note the BAL rating)
- Opening width at top, middle and bottom, and height on both sides
- Floor covering and floor clearance
- Door thickness: 35mm internal, 40mm entrance, 45mm BAL40
- Hinge side and swing (see door handing explained)
- Existing jamb, or a new Prehung jamb or entrance frame
Ready to order? Browse internal doors and entrance doors in standard sizes, or send your measurements through our quote form for a made to order size. Prefer to talk it through? Call 0450 800 088.