How roll-ups and loose tobacco are counted

What counts as loose tobacco?

Here, loose tobacco means tobacco for rolling your own cigarettes (roll-ups), as opposed to ready-made cigarettes. The calculator’s cigarette step says: “Roll-ups? Use loose tobacco and enter how much tobacco you used a week.”

FAQ 5 notes that the use of loose tobacco can complicate what seems a simple calculation. The calculator asks for the weight of tobacco, not the number of roll-ups.

How does the calculator count it?

• 25 g (1 oz) of loose tobacco counts as 50 cigarettes.
• In grams, 1 g counts as 2 cigarettes. In ounces, 1 oz counts as 50.
• The amount is entered per week, so the calculator divides it by 7 to give cigarettes a day.
• It then multiplies by the number of years, adds any other periods and types, and divides by 20.

Where does 50 cigarettes come from?

It is one of the conversion figures taught at the National Respiratory Training Centre at Warwick, England. The References page says: “Loose tobacco estimates that 25 grams (1 oz) has been approximated to be the equivalent of 50 cigarettes.” The original work behind the figure could not be found, but the authors kept it because large numbers of practice nurses had been trained using it.

The References page lists Wood DM et al, “‘Pack year’ smoking histories: what about patients who use loose tobacco?”, Tobacco Control 2005;14(2):141-142, as one of two sources used to check that the figures were close to those of others working in this area. The report found that 12.5 g or half an ounce of loose tobacco was approximately equivalent to one packet of 20 cigarettes.

How do I enter roll-ups in the calculator?

1. In the calculator, on “What have you smoked?”, tick Loose tobacco. If you also smoked ready-made cigarettes, tick Cigarettes as well.
2. On the loose tobacco step, enter the weight used each week and choose grams a week or ounces a week. Grams are selected to start with.
3. Enter the number of years. Use a decimal point for part years, for example 2.5.
4. If the amount changed, choose Add another period and enter each amount with its own years.

More help: the Instructions page, and entering a smoking history that changed for periods and gaps.

What does 50 g a week for 21 years come to?

• 50 g × 2 = 100 cigarettes a week.
• 100 ÷ 7 = 14.29 cigarettes a day, to two decimal places.
• Over 21 years: 100 × 21 ÷ 7 = 300.
• 300 ÷ 20 = 15 pack years.

At the calculator’s rates, 2 oz a week counts the same as 50 g a week (100 cigarettes), so 2 oz a week for 21 years also gives 15 pack years.

What are the limits?

The References page says: “This is not an exact science and approximations have been made.” Because the calculator counts the weight of tobacco, the number and size of roll-ups made from it do not change the result.

Pack years are a record of past smoking, not a diagnosis. If you are worried about your health, speak to your GP practice or use NHS 111. For every conversion figure, see how the calculation works.