Aluminum Door Measurement Guide: How to Measure for Standard & Custom Sizes
Before you order an aluminum entry door, the single most important step happens in your own hallway or on your porch: measuring the opening correctly. Aluminum doors for modern villas, apartments and coastal homes are usually made to measure, which means a measurement mistake can turn into a delayed delivery, a door that does not close properly, or a costly rework. This guide walks through what to measure, how to do it step by step, and when a custom size makes more sense than a standard one.
Why Accurate Measurement Matters for Aluminum Doors
Unlike stock doors that are trimmed on site to fit, most aluminum entrance doors are fabricated with the frame and door leaf matched to your exact opening. The profile is cut, the frame is welded or corner-braced, and the hinge positions are set in the factory. If the width you send is 10 mm too small, the door arrives undersized and the air and water seals no longer line up. If it is too large, the frame may not fit into the opening at all.
Accurate numbers also decide which door configuration works for you. A single leaf is usually the most practical up to roughly 1.1 m of clear width, while wider villa entrances typically move to double doors or pivot doors with their own structural requirements. Measuring first keeps you from choosing a door style that your opening cannot accept.
Tools You Need Before You Start
- A steel tape measure at least 3 m long, not a fabric tape that stretches.
- A spirit level (600 mm or longer) to check whether the sill and header are level.
- A pencil and paper, or a phone, to record every reading on a simple sketch.
- A straight edge, useful for checking whether the frame legs and header are plumb and straight.
- A camera for reference photos of the opening, the surrounding wall and the existing door swing.
Door Leaf, Frame and Rough Opening: Know the Three Numbers
There are three different dimensions in play, and mixing them up is the most common source of ordering errors.
| Dimension | What it means | When you need it |
|---|---|---|
| Rough opening | The raw hole in the wall, masonry or stud frame, measured from structure to structure. | When the supplier builds a full frame with installation clearance. |
| Frame size | The outside dimensions of the aluminum frame that will be fixed into the opening. | Almost always quoted in custom door orders. |
| Door leaf size | The moving door panel itself, excluding the frame. | For replacement panels or when the frame is kept. |
For a full new entry door with frame, the supplier needs the rough opening dimensions plus your wall thickness. The factory then calculates the frame and leaf sizes, including the small installation gap that is later filled with expanding foam or sealant. If you only have the leaf size of an old door, say so in your inquiry instead of guessing the opening size.
How to Measure an Aluminum Door Opening, Step by Step
- Measure the width in three places. Take the opening width at the top, in the middle and near the floor. Record all three and use the smallest value as your reference, because the narrowest point is what the frame must pass through.
- Measure the height on the left, in the centre and on the right. Use the smallest height as the reference. Note whether the floor slopes or whether a threshold will be added later.
- Measure the wall thickness at several points through the opening. Frame depth is sized to the wall, so this number is as important as width and height.
- Check square and level. Compare the two diagonals of the opening; a large difference means the opening is out of square and should ideally be corrected before installation, not absorbed by the door frame.
- Record the details around the opening. Note the type of wall (brick, block, timber, concrete), the available headroom inside and outside, and any step or step-down at the sill.
- Photograph the opening straight on, and add the numbers to the sketch. Suppliers can then confirm the measurements before production starts.
Working rule: measure the opening, not the old door. Width and height are taken in three places each, and the smallest reading becomes your reference. When in doubt, share a photo and the raw numbers with the factory so the frame calculation is done against real conditions.
Door Styles That Change How You Measure
The measuring principles stay the same, but every door type adds one or two details of its own.
Glass entry doors: confirm whether glass panels are glazed into the frame before delivery, and record the opening direction and any mullion that the glass will span.
Double doors: measure the full opening from jamb to jamb and note which leaf should open. The active leaf width and the astragal or centre seal are decided by the factory from your single opening width.
Pivot doors deserve a special note. Because they rotate around an axis instead of side hinges, they need floor and header clearance and generous opening width. If you plan a pivot door, order the structural survey together with the measurements, because the floor and header must be able to carry the door weight.
Standard Sizes vs Custom Sizes: What to Order
Common single entry door openings in many markets fall around 900–1000 mm wide and 2100–2400 mm high. When your opening sits inside a standard range and the wall is square, a stock-size door is quicker and cheaper. When the opening is wider, taller, angled, or part of a villa façade with large format panels, a custom size is the only way to keep the design and the weather seals correct. Most aluminum door manufacturers, including Landran Door, build to the exact dimensions you supply, so a measured drawing removes almost all guesswork from the order.
Common Measurement Mistakes to Avoid
- Measuring only once and trusting the single number.
- Measuring over a door threshold, floor tiles or carpet that will be changed later.
- Forgetting to note whether the old opening is square and level.
- Mixing units, such as writing centimetres in a drawing that is otherwise in millimetres.
- Ordering from the leaf size of an old door while asking for a complete new frame.
- Leaving out wall thickness, which decides the frame depth and the weather performance.
Frequently Asked Questions
Should I measure the rough opening or the finished opening?
Send the rough opening dimensions from structure to structure, together with wall thickness. The frame is then calculated with a correct installation gap for foam, sealant and adjustments.
What happens if my opening is not square?
Small deviations can be absorbed by the frame adjustment during installation. Large deviations should be corrected in the wall first; do not rely on the door frame to hide an out-of-square opening.
How do I measure for a double aluminum door?
Measure the full opening width, height and wall thickness in the same three-point way, and state which leaf must be the active opening leaf. The factory divides the width between the two leaves.
What tolerance should I allow?
Do not add or subtract a tolerance yourself. Supply the measured opening and let the factory apply its own frame and gap calculation, which is based on the profile system being used.
Can I order a non-standard or oversized door?
Yes. Non-standard and large format doors are produced to your dimensions. For oversized or pivot doors, confirm the floor and header structure at the same time as you send the measurements.
Summary: A Measured Door Is a Door That Fits
An accurate set of measurements is the cheapest insurance you can buy for an aluminum entry door. Take width and height in three places each, use the smallest readings, record wall thickness, check the diagonals, and photograph the opening. Then choose your door style with confidence and send the numbers to the factory for confirmation. If you are unsure about any reading, ask the manufacturer before production, not after the door has been shipped.
Ready to compare door styles and opening requirements? Browse the aluminum door catalog or send your measured drawings and opening details for a project review.
