Pole diameter & curtain weight
Diameter is a load rating as much as a look. Here is how to match pole thickness to the weight of the curtain and the width of the window, so nothing sags.
Diameter looks like an aesthetic choice, and it is partly that, but mostly it is a load rating. A pole that is too slim for its curtain will bow in the middle over time, however well it is fitted. Match the thickness to the weight and the span and the pole stays straight for the life of the scheme. Here is how the sizes compare.
The common diameters
- 19mm: slim and understated. Suited to lighter curtains, voiles and modest windows. Elegant on a small window; out of its depth on a heavy, wide one.
- 28mm: the all-rounder. Handles medium-weight curtains on typical domestic windows and is the most widely specified diameter.
- 35mm: substantial. The choice for heavier and interlined curtains and wider windows, and available in longer lengths for bigger spans.
- Timber poles: thicker again, reading as period or statement; their diameter is as much about proportion as load.
The principle is simple: heavier fabric and wider windows want a thicker pole. A grand triple-pinch-pleat, interlined curtain on a 2.4m window has no business on a 19mm pole, however pretty.
Diameter, span and support go together
Thickness alone does not stop a pole bowing; support spacing does the rest. The wider the window and the heavier the curtain, the closer the brackets need to sit, and a long pole often needs a centre bracket as well as the two ends. Our bracket spacing guide sets out the distances; treat diameter and support as one decision, not two.
Beyond load, diameter sets the visual weight. A slim 19mm pole can look lost on a tall, wide window; a chunky 35mm pole can overpower a small one. Pick the diameter that carries the curtain and suits the scale of the window.
When to stop using a pole
There is a point where no pole is the right answer:
- The span is so long that even a thick pole would bow between supports: walls of glass and bi-fold runs.
- You want the rail to be invisible, ceiling-fixed and silent.
- You need cording or motorisation for a high or heavy curtain.
At that point a track takes over. See pole or track and, for the big openings, measuring for bi-folds and large glazing.
One detail for eyelet curtains
If the heading is eyelet, the eyelet must suit the pole diameter: a larger ring for a thicker pole, so the curtain passes freely and glides rather than catches. It is a small specification point that ruins the effect if it is overlooked.
Common questions
What curtain pole diameters are there?
The common metal diameters are 19mm, 28mm and 35mm; timber poles run thicker still. Slimmer poles suit light curtains and shorter spans; thicker poles carry heavier curtains over wider windows.
Which diameter for heavy curtains?
For heavier or interlined curtains, and wider windows, a 35mm pole (or thicker timber) is the safer choice and is available in longer lengths. Lighter curtains on a modest window are fine on 19mm or 28mm.
When should I stop using a pole?
When the span is long enough or the curtain heavy enough that even a thick pole would bow between brackets, or where you want an invisible rail or motorisation, that is the point to move to a track.
Does diameter affect the eyelet size?
Yes. Eyelet curtains must have an eyelet sized to pass over the pole comfortably, for example a larger eyelet for a 35mm pole, so the curtain glides rather than binds.