Wallpaper Calculator: Rolls from Drops, Height and Pattern Repeat

What it calculates

For the walls of a room covered in wallpaper or vinyl wallcovering, the calculator gives:

• the drop length, with pattern repeat and trim;
• the number of drops each roll yields, and the length left over;
• the number of drops needed for the net wall width;
• the rolls to order, before and after a spare allowance.

Inputs

Total width of walls to cover is in metres: the room perimeter, or the walls being papered added together. The equivalent in feet is shown under the field.

Wall height is from the skirting to the ceiling or cornice.

Width of openings to deduct is the total width of doors and other full-height openings.

Pattern repeat is in centimetres, from the roll label; 0 for a plain or free-match paper.

The assumptions panel holds the roll width and length, the trim allowance per drop and the wastage and spare allowance.

Method

1. Net width = wall width − openings.
2. Drop length = wall height + pattern repeat + trim.
3. Drops per roll = roll length ÷ drop length, rounded down.
4. Drops needed = net width ÷ roll width, rounded up.
5. Rolls = drops needed ÷ drops per roll, rounded up.
6. Rolls to order = rolls × (1 + allowance), rounded up.

Finished wallpapers and wall vinyls in roll form are specified under EN 233, and heavy duty wallcoverings under EN 259-1. The roll size is on the label or data sheet.

Assumptions

Limitations

• Openings are deducted by width only. Paper above and below windows and over doors is counted as full drops, which slightly overstates the need.
• Leftover lengths are not reused. Short pieces can sometimes fill over doors or under windows; the calculator does not count them.
• Half-drop and offset matches can waste more than a straight match on some walls. The drop method with one full repeat per drop usually covers them, but check the label.
• Sloping ceilings, stairwells and feature walls need drops of different lengths; calculate each wall separately.
• Adhesive, lining paper and wall preparation follow the product's data sheet and are not counted.

Worked example

Walls 18 m wide in total, 2.7 m high (8.9 ft), one 0.9 m door, 0.53 × 10.05 m rolls with a 32 cm pattern repeat, 10 cm trim and a 5% allowance:

The room needs 11 rolls, so order 12 from one batch. Each roll leaves 0.69 m over after three drops. The net wall area is 46.2 m² (497 sq ft), which by area alone would suggest only 9 rolls. With a plain paper the drop falls to 2.8 m but a roll still yields only 3 drops, so the count does not change; at a 3.0 m wall height with the same repeat, only 2 drops fit in a roll and the order rises to 18.

How engineers use it

On a fit-out, wallcoverings are scheduled on the finishes layout by wall, with the product, roll size, repeat and match. The installer works out drops wall by wall from the drawings, plans where the pattern starts so it is centred on feature walls, and orders whole rolls from a single batch with a few spares kept on site for repairs.

When a professional design must replace it

Use the calculator to estimate rolls for a simple room or check a supplier's figure. Replace it with a wall-by-wall take-off from the installer before ordering, and wherever the wallcovering has a large or offset repeat, is a wide-width commercial product, covers tall or irregular walls, or must meet a reaction-to-fire class set by the project's fire strategy. That class comes from the product's test classification and the designer, not from this calculation.