How the cost is worked out
cost per day = cigarettes a day ÷ cigarettes per pack × price of a pack
A year is 365.25 days. The "invested" figures assume the monthly amount goes into a fund returning 8% a year — roughly a long-run stock-market average — with returns reinvested.
Common questions
Where does the 8% investment return assumption come from?
It's a commonly used rough estimate for the long-run average annual return of a diversified stock index, before inflation — real returns vary a lot year to year, so treat the "invested" figures as illustrative, not a forecast.
Does this account for inflation?
No — both the cost projections and the investment growth are in today's money terms; it doesn't model rising cigarette prices or inflation eating into investment gains over time.
Money figures are estimates from the numbers you enter. Investment growth is illustrative, not guaranteed.