A metre of film has a width
Read length and width together. A longer roll is not necessarily more film area if it is narrower. The selected Waitrose roll declares 40 m length and 350 mm width, approximately. A comparison based only on 40 m would omit an important field. Keep any alternative’s exact current width rather than assuming all domestic cling film is the same.
Convert the declared width correctly
For this selection, 350 mm is 0.35 m, so the declared nominal geometric area is 14 m². At£2.50, the arithmetic is£0.0625 per declared metre or about£0.178571 per declared square metre. These are derived comparison rates, not separate retail units or a measurement of the received material.
Do not count area as successful coverage
Useful coverage can be less than geometric area because a task may require overlap or leave trim. We provide no bowls-per-roll, food-portion count or adhesion-efficiency estimate. Nor does the area rate establish food-contact, freezer or microwave suitability. Those fields require the selected product’s actual instructions.
Refuse unsupported units
The cost tool offers length/area bases only for the known film record and refuses them for a counted bag pack. The stock tool can buy whole film rolls for a chosen declared-metre target, with surplus shown. It does not convert a bin liner’s nominal litres or a zipper bag’s flat size into comparable film area.
A purchase case to keep explicit
For a film-length comparison, keep millimetres and metres explicit.350 mm is 0.35 m, not 350 m. The derived 14 m² describes nominal geometry only. An intended task may need overlap or leave trim, and no actual bowls-per-roll result has been measured.
Sources & scope
Checked November 5, 2026. Manufacturer and retailer references support the specific statements. Dated displayed prices are not final checkout quotes, performance rankings or performance testing. This shopping reference does not replace the exact product label or retailer instructions. Current received labels and independent materials/food-contact/content/commerce review remain pending.