Curtain Size Lab Search

HARDWARE GUIDE · REVIEWED SEPTEMBER 11, 2026

How Far Should a Curtain Rod Extend Past the Window?

Compare editable side-extension ranges and calculate rod working length without treating one convention as a rule.

MEASURED WIDTHFINISHED DROP
Original proportional diagram. Use actual measurements; drawing is not to scale for a specific product.

SHORT ANSWER

Start here

Six inches (about 15 cm) per side is a common published starting point, and John Lewis presents 15–20 cm (6–8 in). Treat that as a planning range, not a universal rule: wall space, stack-back, returns, and the chosen hardware determine the real extension.

IKEA example6 in each side
John Lewis range6–8 in each side
FormulaWindow + left + right
FinialsAdd separately

How to measure

  1. 01

    Measure the actual working rod or track width; if hardware is not installed, record the window-frame width and your planned side extensions separately.

  2. 02

    Measure the drop from the reference point stated for the selected heading—not from an unrelated edge of the window.

  3. 03

    Check whether a package contains one panel or a pair, then compare total flat fabric width rather than the label width alone.

  4. 04

    Recheck the selected product, tape, hooks, carriers, and fabric before ordering or cutting.

Why side extension matters

Extension can help the curtain cover the frame at the edges and lets more glass remain exposed when panels are open.

When six inches is not enough

Wide, thick, lined, or high-fullness panels can occupy more wall space when open. Use a physical fold sample or system stack chart for a critical opening.

When space is limited

A nearby wall, cabinet, or corner may cap the available extension. Reduce the assumption in the calculator and check that the closed panels still cover the intended opening.

Before you order or cut

Measure the actual window and selected product. Finished sizes, fullness, header take-up, hardware geometry, and manufacturer tolerances vary. Fabric can shrink, stretch, or behave differently by composition. Measurements do not guarantee fit, privacy, water containment, installation, load capacity, or structural safety. Use the selected product instructions, and have a professional workroom verify expensive custom-fabric orders.

SOURCE NOTES

What this page is based on

Measurements here combine mathematical results with labeled commercial conventions and design recommendations. Disagreements are kept as ranges rather than averaged into a false standard.

  1. BETYDLIG/RÄCKA/HUGAD buying guide — Measure your windowIKEA · reviewed 2026-09-11

    Primary manufacturer guide: add at least 6 in each side, add 6 in above, and use 2–2.5× rod width for panel planning.

  2. Buying curtainsJohn Lewis & Partners · reviewed 2026-09-11

    Retailer/workroom guidance on pole extension, hanging references, sill/floor endpoints, ready-made metric ranges, and double fullness.

  3. VIDGA — How to measure your windowsIKEA · reviewed 2026-09-11

    Current manufacturer track-system guide with measured-window diagrams, minimum side extension, stack-back planning, and hanging-point length references.