How deep should a pelmet be?

As a rule of thumb a pelmet sits at roughly 1/5 to 1/6 of the finished curtain drop, so 35–42cm for a 210cm drop. Aim for at least 25–30cm so the fabric covers the curtain track and heading tape. This calculator accepts depths from 15cm (for very short windows) up to 60cm, but most pelmets on standard windows look best at 25cm or more. Shaped pelmets can be deeper at the centre.

How far should a pelmet extend beyond the window?

The pelmet board should extend 10–15cm beyond each side of the curtain track so the drawn-back curtains tuck behind it. The return (the depth from the wall, set with the Return Depth input) needs to clear the curtain stack — typically 12–18cm, with 15cm a safe default.

What is the difference between a padded and buckram pelmet?

A padded pelmet is soft, with wadding behind the fabric for a plump look. A buckram pelmet uses stiffened pelmet buckram for a rigid, structured shape and can be cut into a decorative shaped lower edge. Both wrap a face and a backing, so this calculator allows twice the depth plus turnings for the fabric height.

Why does the fabric quantity depend on the fabric width?

A pelmet piece is wide (board length plus returns) but not very tall. With plain furnishing fabric the piece is usually "railroaded" — cut sideways along the length of the bolt — so you buy the piece WIDTH in metres. With patterned or directional fabric the pattern must run upright, so the piece is made from joined drops cut across the standard 137cm bolt; you then buy drops × the cut drop. Turn on "Patterned / directional fabric" to switch the calculation to joined drops.

Do I need a pelmet board?

Yes, a pelmet board is essential. Use 15–18mm MDF or plywood. The board mounts above the window on angle brackets, and the pelmet fabric attaches to the board with hook-and-loop (Velcro) tape for easy removal and cleaning.

Pelmet Calculator — Fabric & Board Dimensions

Calculate fabric and board dimensions for pelmets and valances.

Window Width

Measure the curtain TRACK width, not the glass. The board should clear the track by ~10–15cm each side.

Pelmet Depth

The drop of the pelmet face. Aim for ~1/6 of the curtain drop and at least 25cm to hide the track and heading.

Return Depth

The board projection from the wall. Use 10–15cm so drawn-back curtains clear the pelmet.

Pelmet StylePadded and buckram wrap a flat face; gathered adds fullness for a soft ruched valance.

Fabric WidthWidth of the fabric bolt. Most UK furnishing fabric is 137cm (54in) wide.

Patterned / directional fabric

Turn on if the design must run upright (so the piece is made from joined drops rather than railroaded). Add one pattern repeat per drop when buying.

Fabric Price (optional)

Price per metre of your chosen fabric, to estimate the cost.

How We Calculate This

Pelmet dimensions come from the curtain-track width plus the side returns. The cut fabric piece is sized from the style, then the metres to buy depend on whether the piece is railroaded (plain fabric) or made from joined drops (patterned fabric).

The formula

Board length = Window/track width + (Return depth × 2)

Padded/Buckram piece: Width = Board + 10cm, Height = Depth × 2 + 10cm

Gathered piece: Width = Board × fullness, Height = Depth + 20cm

Plain fabric (railroaded): Metres = Piece width × 1.1 ÷ 100

Patterned fabric: Drops = ⌈Piece width ÷ Fabric width⌉, Metres = Drops × (Piece height + 20cm) ÷ 100

Frequently Asked Questions

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Last updated: June 2026

All calculations are estimates. Always verify quantities before cutting or purchasing fabric.