How to Measure Curved Aluminum Work for an Accurate Price Estimate: A Checklist for Technicians Before Sending the Design

To measure curved aluminum work for an accurate price estimate, you need to measure more than just width × height. Six key points must be specified: opening width (measured at multiple points), total height, straight-section height before the curve begins, curve radius, curve style, and wall depth. Photos of the site and the preferred window or door system should also be provided. The more complete the information, the more accurate the price estimate and the lower the chance of production errors.

Curved aluminum work is not the same as standard straight-frame work. Sending only “width × height” to the supplier is often not enough for price estimation and actual production, because curved work has additional variables that affect both the price and the accuracy of the design.

This article is created especially for technicians and contractors. It covers measurement methods, key points that must be clearly specified, and a checklist before sending the design, so the supplier can estimate the price more accurately and reduce the chance of repeated corrections.

Why is curved aluminum work harder to measure than straight work?

Straight-frame work usually requires only width and height, but curved work has additional dimensions that must be controlled accurately:

• Curved work has a radius, not just width × height. Different radii can greatly affect the curve shape and the length of the aluminum profile.
• The curve starting point must match both the design and the actual opening. If the curve starting point is off, the entire panel shape can become distorted.
• The frame and glass must align correctly. Curved glass must be cut to match the frame radius precisely. Even a small error can prevent the glass from fitting into the groove.
• If the measurements are incorrect, the assembled work may not fit tightly, and gaps between the straight section and curved section can become clearly visible.
• If the radius is inaccurate, the glass may not fit into the groove, or the seal line may not be complete, which can lead to leakage.

What should be measured before requesting a price estimate for curved aluminum work?

6 key measurement points technicians should collect before sending the design:

1. Opening Width

Measure the left-to-right distance of the opening. It is recommended to measure at multiple points, such as the top, middle, and bottom, to check whether the opening is square. If the measurements at all 3 points are different, it means the opening may be tilted or the wall may not be straight. This should be reported to the supplier so they can allow for adjustment.

2. Total Height

Measure from the floor or bottom edge up to the highest point of the curve. This is used to calculate the overall frame size. This measurement includes both the straight section and the curved section.

3. Straight-Section Height Before the Curve Begins

This point is very important and is often overlooked by technicians. It indicates where the curved section starts. If it is not specified, the supplier will have difficulty determining the curve shape and may produce a frame with proportions that do not match the required design. The correct way to measure it is to measure from the bottom edge up to the point where the straight line begins to curve.

⚠️ The curve starting point, or Spring Line, is the variable that most often causes curved work to become inaccurate. A semicircular arch and a top arch with the same width but different curve starting points will result in completely different shapes.

4. Curve Radius

If there is a CAD drawing or a hand-drawn plan with clearly specified dimensions, it should be sent to the supplier along with the curve radius. CAD provides more accurate dimensional data than photos, helping the supplier create the design, estimate the price, and plan the frame bending more accurately.

However, if there is no CAD drawing, send the actual opening dimensions, the straight-section height before the curve begins, and site photos from multiple angles instead. The supplier can use this information to review the proportions and calculate the initial curve radius.

5. Curve Style

Clearly specify the type of curve, because each style requires a different bending and calculation method:

• Segmental Arch: a shallow curve with a radius larger than the opening width
• Semicircle: the radius equals half of the opening width
• Elliptical Arch: the horizontal and vertical radii are different
• Full Circle: a round fixed glass opening
• Multi-radius Curve: a custom freeform curve that requires a specific drawing

6. Wall Depth or Installation Distance

This helps the supplier estimate the installation method, frame size, and edge finishing more accurately, especially for work that requires the frame to be embedded into the wall or where an existing frame is already in place.

What information should be sent to the supplier if there is no CAD drawing?

Many technicians worry that they cannot request a price estimate without a CAD drawing. In fact, an initial estimate can still be requested if complete photos and information are provided.

Checklist When There Is No CAD Drawing

How does the window or door system affect size measurement?

The window or door system should be selected before taking the final measurements, because each system requires different clearance allowances. If the system is changed after measurements have already been taken, the usable frame size may also change, especially for work that requires allowance for sliding tracks or projects that combine fixed glass panels with casement panels in the same frame.

Fixed curved transom window

This is the easiest type to measure among curved work, because there is no need to allow clearance for hinge hardware, rollers, or locks. Measuring only the opening size and curve shape is enough for an estimate.

Arched casement window

Clearance must be allowed for hardware, hinges, locking points, and the space needed to open the panel. Technicians should measure and specify whether the panel opens inward or outward, as well as the opening direction, so the supplier can design the hinge positions correctly.

Arched sliding window

The sliding track distance, panel overlap area, and limitations of the curved shape must be considered. Curved sliding panels can only be made in certain shapes, so technicians should provide the radius for the supplier to check feasibility first.

Curved Doors

The panel weight, actual height, load-bearing points, and suitable locking hardware for curved work must be considered. Curved doors are heavier than windows, so technicians need to measure and specify all structural information to select the right load-bearing hardware.

Common mistakes technicians often encounter when sending measurements for curved work

• Sending only width × height without specifying the curve starting point, causing the supplier to assume the wrong curve shape
• Not specifying whether the required system is a casement panel, sliding panel, or fixed glass panel, even though the price and clearance allowances are very different
• Not specifying the radius or curve shape, resulting in a highly inaccurate price estimate
• Measuring from an opening before plastering is complete, as the dimensions may change after plastering and cause the finished frame to not fit properly
• Not checking whether the opening is square, as a tilted opening makes curved work harder to install and can look asymmetrical
• Not providing site photos, preventing the supplier from seeing the actual installation limitations
• Not specifying the frame color, glass type, and number of pieces, causing the supplier to ask for more details and estimate again, which wastes time for both sides

Tools and methods for measuring curve radius on an actual site

Method 3: Taking photos with a scale reference

Method 4: Sending a CAD drawing or architectural drawing

Checklist of information to send to SGQ before estimating curved work

Summary table of information to send and why each item is important:

How to measure curved aluminum work for an accurate price estimate

Curved work requires more measurements than straight work, especially these 4 points that technicians often overlook:

• Curve starting point (Spring Line): indicates where the curve begins
• Curve radius and curve style: semicircle, segmental arch, elliptical arch, or multi-radius curve
• Panel system: fixed panel, casement panel, sliding panel, or door — each requires different clearance allowances
• Squareness of the opening: measure at multiple points to check whether the wall is straight.

If the information is complete from the beginning, the supplier can estimate the price more accurately, reduce the chance of producing the wrong design, and help technicians plan the installation more easily. This saves both time and the cost of repeated corrections. In addition to accurate measurement, clear communication with the supplier from the start is equally important. If the information sent does not match what the supplier understands, there is a higher chance that the final work will not match the required design, even if the measurements are correct.

Send your curved work design to SGQ for assessment

Have a curved window, curved door, or curved fixed glass panel that needs design preparation? Send site photos, opening dimensions, and the desired design to the SGQ team for an initial assessment. Our team supports technicians and contractors, and is ready to provide advice on measuring and preparing designs for curved work.