Curtain Calculator UK — Fabric Width & Drop

How Curtain Fabric Quantities Are Calculated

Curtain fabric requirements depend on three key measurements: the pole or track width, the drop length from the top of the heading to the desired hem point, and the fullness ratio determined by your chosen heading style. A pencil pleat heading typically requires fabric at 2 to 2.5 times the pole width, while a pinch pleat needs around 2 times. Eyelet curtains are the most economical at 1.5 to 2 times the pole width. Tab-top curtains need the least fullness, usually 1.5 times.

For each curtain, add allowances for side hems (usually 5 to 8 centimetres on each side) and the bottom hem (10 to 15 centimetres). If your fabric has a pattern repeat, you must factor this into each drop length, which increases the total fabric needed. The calculator handles all of these adjustments for you when you enter your measurements and select your heading type.

Choosing Curtain Fabric and Linings

The weight and drape of your fabric affects how the finished curtains look and perform. Lightweight fabrics like voile and cotton work well as unlined panels that filter light gently. Medium-weight fabrics including linen blends and polycotton suit most living spaces when lined. Heavier fabrics such as velvet, chenille and brocade create a luxurious look and provide excellent thermal insulation, particularly important during cold UK winters.

Lining your curtains improves their hang, protects the face fabric from sun damage, and adds a layer of insulation. Blackout lining is ideal for bedrooms, while thermal lining helps reduce heat loss through windows. Interlining, a soft padding sandwiched between the face fabric and lining, creates the ultimate in luxury and warmth but significantly increases the cost and weight of the finished curtains.

Measuring Your Windows Correctly

Always measure with a steel tape measure rather than a fabric one for accuracy. For the width, measure the pole or track from end to end, not the window frame. The drop should be measured from the top of the pole for eyelet curtains or from the bottom of the rings for other styles. Floor-length curtains should finish 1 to 2 centimetres above the floor to avoid dragging, unless you want a puddled effect.

If you are also considering blinds or need to plan around radiators, our radiator BTU calculator can help you check whether curtains covering a radiator will affect heat distribution. Use the room area calculator for whole-room planning. For energy-saving advice, visit GOV.UK.