How to correctly measure a garage door: 5 steps to prevent an incorrect order

Properly measuring a garage door means determining: clear width, clear height, lintel height, reveal width, and garage depth. All dimensions should be given in millimeters and measured at a minimum of 3 points. Sectional doors require a lintel of 150–230 mm. Roller doors can work with as little as 160 mm. Anyone who overlooks the final finished floor level risks placing an incorrect order.

Key points at a glance

Always provide all dimensions in millimeters, not centimeters.
Measure each dimension at 3 points and use the smallest value.
The clear opening (clear width/height) and the order size differ by 10–40 mm.
Sectional doors require a lintel of 150–230 mm; our RGW roller doors start from 160 mm.
Always measure height from the finished floor level, not from the subfloor.

What do structural opening size, clear opening, and order size mean?

Most people confuse these three terms — and this is exactly where the most costly mistakes occur. Let’s clarify them briefly.

The structural opening size (Rohbaumaß) refers to the dimensions of the opening after masonry work, in its unfinished state — with no plaster, no screed, and no final layers. For example: 2,520 mm in width.

After plastering and installing the floor, the opening becomes smaller. The remaining usable space is called the clear opening (Lichtmaß). In our example, this would be around 2,480 mm. This is the actual space your car will pass through.

The order size (Bestellmaß) is different again. The manufacturer requires a specific value that takes installation tolerances and side clearances into account. For the K2 RFS 60 sectional door, the order size is typically the clear opening + 20 mm in width. Depending on the door type, the difference between the clear opening and the order size is usually 10–40 mm.

Term	Meaning	Example
Structural opening size	Opening before plaster and screed	2.520 mm width
Clear opening	Usable opening after completion	2.480 mm width
Order size	Value for the manufacturer	2.500 mm

Anyone who wants to compare all available garage door models, including their respective order formulas, can find a complete overview on the Garage doors from Poland page.

How to properly measure a garage door? 5 steps

Now let’s get practical. Take a measuring tape and a pen. Really — don’t try to estimate it by eye.Garage walls are rarely perfectly straight. From top to bottom, they can differ by 10–30 mm. That’s why for every step the rule is: always measure at 3 points and always record the smallest value.

One more important thing before you start:

If you are planning an electric operator — for example, models from the Modern garage door operators for your home overview — it requires additional space above the door. Make sure to take this into account already in step 3!

The 5 measurement steps

Measure the clear width — from the left to the right inner edge of the wall, at 3 points (top, middle, bottom). Record the smallest value.

Measure the clear height — from the top edge of the finished floor to the underside of the lintel, at 3 points (left, middle, right). Record the smallest value.
Important: only measure once the floor is finished.

Measure the lintel height — the free space between the underside of the lintel and the garage ceiling.

Sectional door: 150–230 mm
Roller door RGW: from 160 mm
With electric operator: add +80–150 mm

Measure the internal reveal widths — the narrow wall sections on the left and right sides of the opening where the guide rails and frame will be installed. Measure both sides separately.
Standard tracks require at least 90–100 mm.

Measure the garage depth — the internal depth from the door opening.
Formula: door height + at least 1,200 mm without an operator
With operator: door height + 1,300 mm

Each of these 5 steps has its own potential source of error. The most common mistakes are listed below. If you have all 5 values correct, you can pass the measurements directly to the supplier.

What does the floor have to do with measuring?

This is where the most common mistake in self-measurement occurs. Many people measure the height from the subfloor — and then order a door that jams after the screed is installed. A typical screed build-up is 50–80 mm. That is not a small difference.

A door that jams cannot be shortened afterwards. It must be reordered, which costs time and money. The solution is simple: always measure the height from the finished floor level.

What to do in practice:

Floor already finished? Measure from the final surface.
No floor yet? Subtract the planned floor build-up — e.g. 60 mm for screed.
In case of slopes or uneven surfaces: use the lowest point of the entrance as the reference.
If in doubt: have the measurements taken by a professional company.

Which dimensions apply to which door type?

This is a crucial point that hardly anyone explains — yet it determines everything. Sectional doors, roller doors, and up-and-over doors require completely different spatial conditions.

Sectional door: 150–230 mm lintel, 90–100 mm side reveals
Roller door RGW: lintel from 160 mm
Up-and-over door: up to 300 mm lintel and an additional 1,000–1,200 mm depth beyond the door height

Anyone who uses the wrong values for their door type risks construction modifications costing €500–1,500.

Is your lintel lower than 200 mm?

Then a sectional door is mechanically not feasible. The solution is a roller door.
If there is no space inside, a RGZ roller door with external box is an option — see the overview on the Roller doors for every application page.

Electric RGW roller doors without a box require a lintel height of at least 160 mm. That is up to 70 mm less than a sectional door. In many older buildings, this difference determines which type of door can be installed at all.

Comparison table: Which door type is suitable for which garage dimensions?

Requirement	K2 sectional door	RGW roller door	RGZ roller door
minimum lintel height	150–230 mm	160 mm	0 mm (external box)
minimum reveal width	90–100 mm	60–80 mm	60–80 mm
minimum garage depth	height + 1.200 mm	height + 400 mm	height + 400 mm
thermal insulation	up to U = 0,98 W/m²K	no thermal insulation (uninsulated)	no thermal insulation (uninsulated)
RC2 burglary protection	optional, TÜV-certified	no	no

Which door is suitable for your project? 5 decision rules

Lintel height below 200 mm (inside): choose an RGW or RGZ roller door. A sectional door cannot be installed mechanically.

Lintel height above 200 mm and garage depth at least door height + 1,200 mm: the K2 sectional door is the first choice. It offers thermal insulation up to U = 0.98 W/m²K.

No space in the lintel area inside, but the external façade is accessible: choose the RGZ roller door with external box. No intervention in the wall structure is required.

Existing up-and-over door and looking for a replacement: the K2 sectional door is a direct upgrade. Up-and-over doors require more depth than sectional doors.

Heated garage: only the K2 RFS 60 sectional door makes sense, with U = 0.98 W/m²K. Roller doors are uninsulated (cold doors).

The 5 most common measurement mistakes

Now we come to the part that causes the most problems. These 5 mistakes happen all the time — especially when measuring on your own without a professional service.

Measurement errors occur more often during door replacement than in new builds — you can find all guidance on this topic on the Renovation of your garage door page. The reason is simple: in renovations, you are dealing with an old frame, a floor that may no longer be level, and walls that have settled over time. This complicates measurements — and if you’re not precise, you’ll end up paying twice.

The 5 mistakes and their consequences:

Mistake 1 — measuring from the subfloor instead of the finished floor level:
Always measure height after screed or flooring has been installed. Typical screed build-up: 50–80 mm.
Consequence: the door jams after the floor is finished.

Mistake 2 — measuring at only one point:
Always measure at least at 3 points. For width: top, middle, bottom. For height: left, middle, right. Always use the smallest value.
Consequence: the narrowest point is overlooked and the door does not fit.

Mistake 3 — lintel height without allowance for the operator:
An operator requires 80–150 mm more than the mechanical lintel height alone. For STARCUS models F35, F50, and F70, always check the installation manual in advance.
Consequence: the operator cannot be installed later.

Mistake 4 — forgetting the side reveals:
Measure both sides separately. If one side is less than 90 mm, standard tracks cannot be installed without a special solution.
Consequence: installation fails on site.

Mistake 5 — providing dimensions in centimeters:
Manufacturers work in millimeters. Deviations of ±10 mm already exceed installation tolerances.
Consequence: inaccuracies lead to incorrect production. Always provide all dimensions in mm.

What is different about renovation compared to a new build?

Good question — and one many people only think about when it’s too late. Measurements during renovation are different from those in new construction. The key question is: will the old frame remain, or will it be removed?

If you measure inside the old frame but order a door based on the masonry opening, you’ll have a problem. The new door will be too large for the frame. This happens more often than you might think.

How to proceed correctly:

Old frame remains: measure inside the frame, not the masonry opening.
Old frame will be removed: measure the masonry opening and include installation tolerances.
Remove the old bottom threshold strip and re-measure the height from the top edge of the finished floor level.
During renovation, you can change the door type — for example, from an up-and-over door to a K2 sectional door. In that case, check the new garage dimensions, as each type requires different lintel and depth clearances.

Standard and custom sizes: what do your measurements mean for ordering?

There are 11 common standard garage door sizes in Germany. The most frequent combination is 2,500 × 2,125 mm. With KRISPOL, there are no extra charges for custom sizes — each door is manufactured individually within 2 weeks.

Many garages in Germany deviate slightly from standard sizes — for example, 2,530 mm instead of 2,500 mm. Other manufacturers charge extra for this. With KRISPOL, the rule is: any size, any colour — one price.

Electric RGZ roller doors with an external box are also produced without surcharge in any custom size. This applies to all models. Custom dimensions can be combined with the full colour range for garage and industrial doors — 200 RAL colours and 2,050 NCS colours, also at no additional cost.

The 5 most common standard sizes:

width × height	use
2.250 × 2.000 mm	small single-family house
2.500 × 2.000 mm	most common combination
2.500 × 2.125 mm	standard height for new builds
2.750 × 2.125 mm	entrance width
3.000 × 2.000 mm	double garage

KRISPOL manufactures custom sizes up to 6,000 × 3,000 mm at no additional cost.

Frequently Asked Questions

Properly measuring a garage door means: measuring in millimeters, at a minimum of 3 points, from the top edge of the finished floor level — with separate values for width, height, lintel, reveals, and garage depth. If you are unsure, you can use the Find a Krispol dealer near you page to locate the nearest authorized specialist for an on-site measurement.

1 / What dimensions do I need for a new garage door?
You need 5 measurements: clear width (3 points, smallest value), clear height (3 points from the finished floor level, smallest value), lintel height, reveal width on both sides, and garage depth. All values must be provided in millimeters. Only with all 5 measurements can the manufacturer produce a suitable door.

2 / What is the difference between clear opening and order size?
The clear opening is the actual passage size after completion. The order size differs by 10–40 mm because it includes installation tolerances and the frame. The exact order formula is defined by the respective manufacturer.

3 / How much space do I need above the garage door?

Sectional door: 150–230 mm depending on the spring system
Roller door RGW: from 160 mm
With electric operator: add +80–150 mm
Up-and-over door: 200–300 mm

If you forget to allow space for the operator, it cannot be installed later.

4 / What happens if I measure incorrectly?
The door cannot be installed. Depending on the deviation, structural modifications may be required or the door must be reordered. Therefore, if in doubt, always have measurements taken by a professional on site.

5 / Are there standard sizes, and do I have to use them?
Yes — there are 11 common standard sizes in Germany. The most popular combination is 2,500 × 2,125 mm. With KRISPOL, there are no extra charges for custom sizes. The door is manufactured individually to your exact clear opening within 2 weeks.