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Width of the Glass
Measure straight across the glass from the point where the curve begins on the left to the corresponding point on the right.
How to Measure for an Arch or Eyebrow Curtain Rod
Custom Hardware for Curved Windows
An arch or eyebrow window brings a graceful curve into the room, but a standard straight curtain rod can hide the very shape that makes the window special. A custom curved rod follows the line of the glass while sitting just outside the window frame, allowing the architecture to remain visible.
Measuring the window may look complicated at first, but the process becomes much easier when it is divided into two parts. First, measure the shape of the glass. Then decide where the rod and drapery should sit outside that shape.
Begin with the Glass
Measure the Shape of the Arch or Eyebrow Window
Measure the visible glass area—not the outside of the window trim or molding. The goal is to record the width of the curved opening and the vertical rise from the point where the curve begins to the highest point of the glass.
Height of the Curve
Measure vertically from the horizontal line where the curve begins to the highest point at the center of the arch.
Measurement One
How to Measure Width W
Width establishes the distance between the two points where the curve begins.
Find the Beginning of the Curve
Identify the point on each side where the straight vertical portion of the glass transitions into the curved top.
Measure Straight Across
Measure in a straight, level line from the left beginning point to the right beginning point.
Do not follow the curved edge of the glass with the tape.
Record the Glass Width
Record the measurement in inches and label it clearly as W. Measure it a second time before moving on.
Measurement Two
How to Find Arch Height H
When it is difficult to hold a tape directly from the beginning of the curve to the center peak, the height can be calculated using floor and ceiling reference measurements.
Floor to Curve
Measure from the floor at the side of the window to the point where the curve begins.
Curve to Ceiling
Measure from the side point where the curve begins straight up to the ceiling.
Floor to Peak
Measure from the floor at the center of the window to the highest point of the glass.
Peak to Ceiling
Measure from the highest point of the arch straight up to the ceiling.
Calculate the arch height using either method:
H = C − A
H = B − D
Both calculations should produce the same result. A small difference usually means one of the reference measurements should be checked again.
Keep every measurement vertical and use the same floor or ceiling reference.
Uneven floors, sloped ceilings, thick molding, or measuring from
different reference points can produce conflicting results.
Positioning the Finished Rod
Choose Where the Curved Rod Will Sit
The rod is mounted outside the glass area. The next measurements describe how far it should sit above and beyond the window.
Upper Rod Placement
Measure from the highest point of the arch to the underside of the rod, without including rings.
Drapery Panel Placement
When using rings, measure from the highest point of the arch to the top edge of the finished drapery panel.
Left Extension
Measure horizontally from the left edge of the glass to the base of the left finial.
Right Extension
Measure horizontally from the right edge of the glass to the base of the right finial.
L and R are often the same, but record them separately.
Windows, trim, adjoining walls, or nearby architectural features may
require the rod to extend farther on one side than the other.
Allowing for the Finished Treatment
Rings, Drapery Panels and Rod-End Placement
The final drapery position depends on the rod curve, ring size, panel construction, and the upper placement selected.
Rod Underside vs. Fabric Top
U describes the underside of the bare rod. P describes the top edge of the drapery panel when rings are used. These are not the same location.
Last Ring Position
The last ring is generally located approximately one inch inside the L and R rod endpoints, depending on the rod curve and hardware selected.
Rod Ends May Sit Higher
L and R are horizontal extensions of the width. Depending on the curve and the selected U or P measurement, the rod may not descend fully to those horizontal reference points.
Check Finial Clearance
L and R end at the bases of the finials. Allow additional room beyond those measurements for the finials themselves.
Confirm Panel Construction
Record whether the treatment uses rings, clips, tabs, ties, or another heading so the finished fabric position can be reviewed.
Consider Drapery Function
Curved rods are often used for stationary decorative panels. Discuss the intended movement before ordering when curtains need to open or close across the curve.
From Window Shape to Finished Rod
How the Measurements Work Together
The glass measurements establish the underlying curve. The placement measurements position a larger, offset curve outside the window so there is room for the rod, rings, and fabric.
W and H Define the Window
Width W and arch height H describe the size and rise of the visible curved glass.
U or P Establishes the Upper Offset
This measurement determines how far above the glass the rod or top of the fabric should sit.
L and R Establish the Side Extensions
These measurements determine how far the rod extends beyond the glass before the finials begin.
We Calculate the Finished Curve
Once the window shape and desired placement are known, the rod curve and projection can be calculated for the custom order.
Preparing the Custom Order
What to Send Iron Accents
A clearly labeled sketch and several photographs help us understand the window and identify concerns before production.
Window Measurements
- Width W
- Arch height H
- A and C measurements, when used
- B and D measurements, when used
Placement Measurements
- U for underside of rod
- P for top of drapery, when rings are used
- Left extension L
- Right extension R
Photos and Details
- Full photo of the window
- Close-up of the arch and trim
- Side-wall and ceiling clearance
- Selected ring or heading style
- Any nearby obstructions
Before Submitting the Order
Arch and Eyebrow Rod Measurement Checklist
Glass Shape
- W was measured straight across the glass.
- The beginning points of the curve were identified.
- H was measured or calculated.
- Both height calculations were compared when possible.
- All dimensions are recorded in inches.
Rod Placement
- U or P has been selected and recorded.
- L and R were measured separately.
- Measurements end at the finial bases.
- Finial clearance has been checked.
- Nearby ceiling and side walls were considered.
Drapery Treatment
- Ring or heading style is identified.
- Panel-top placement is understood.
- The intended drapery movement is described.
- Fabric and ring clearance has been considered.
Final Review
- Every measurement was checked twice.
- A simple labeled sketch is included.
- Clear photographs are included.
- Questions were resolved before ordering.
Common Questions
Arch and Eyebrow Curtain Rod Measuring FAQ
Do I measure the glass or the outside trim?
Measure the visible glass area to establish W and H. Separate placement measurements determine how far the finished rod sits outside the glass.
Do I measure along the curved edge?
No. W is a straight horizontal measurement, and H is a straight vertical measurement.
What if I cannot measure H directly?
Use the floor-reference formula H = C − A or the ceiling-reference formula H = B − D. Both should produce the same result.
What is the difference between U and P?
U measures to the underside of the rod without rings. P measures to the top edge of the finished drapery panel when rings are used.
Are L and R included in the window width?
No. W is the width of the curved glass. L and R are additional horizontal extensions beyond the left and right edges of the glass.
Are finials included in L and R?
No. L and R end at the bases of the finials. Allow additional space for the decorative finials themselves.
Why might the rod ends not come down to the exact L and R line?
L and R are straight horizontal extensions. The final endpoint height is also influenced by the curve and the selected upper placement measurement, U or P.
What should I do if the two H calculations do not match?
Recheck A, B, C, and D, making sure each measurement is vertical and taken from the same floor or ceiling reference.
Should I send photographs?
Yes. Include the entire window, the curved glass, surrounding trim, the ceiling above, side clearances, and nearby obstructions.
What should I do if I am unsure about the measurements?
Contact Iron Accents before ordering. Custom curved rods are made to the measurements supplied, so questions should be resolved before production.
Designed Around the Architecture
Let the Curtain Rod Follow the Window
A properly measured curved rod preserves the graceful outline of an arch or eyebrow window rather than covering it with a straight horizontal line.
Review the window measurements, rod placement, rings, drapery construction, and surrounding clearances carefully. Contact the Iron Accents team before ordering whenever the window shape or measurements are uncertain.
