We promised not to lie to you. So here is the arithmetic behind everything shown on the home page: the starting assumption, the sums, the sources, and above all what we do not claim to know.
It all comes from one profile, chosen once and never changed along the way: a pack of twenty cigarettes at €16.80, smoked every day. If you smoke differently the figures move — the app itself uses yours.
Almost all of a pack's price is tax. That is also why the amount climbs faster than inflation: the price follows government decisions, not only the manufacturer's.
This share varies from one country to the next. The calculation above is the one for the country shown on the home page, and it changes with it.
Counted at five minutes a cigarette — the low end of the usual range, which runs from five to seven minutes. At seven minutes every figure below rises by about 40%. We keep the low value: when an assumption flatters the argument, take the one that flatters it least.
The ten-year figure is not ours, and it is not the time spent smoking multiplied out. They are two different measurements: one counts the act, the other the consequence. Two large independent cohorts land on the same order of magnitude.
This is a population average, not a prediction about a person. And it is largely recoverable: according to Jha, quitting between 25 and 34 gives back about ten years, between 35 and 44 about nine, between 45 and 54 about six.
The idea is simple: what you no longer spend, you put away at the end of each month. The calculation is an ordinary annuity, compounded monthly.
The home page shows€210,000, rounded down to the multiple of 5 000 below — never up, since this is a projection and not a promise. The exact amount is €210,038.21. A figure to the penny would give a false impression of precision about something that remains an assumption — whereas in the app, where it is your real money, nothing is ever rounded.
No source publishes an average price for “France excluding Paris”. The national average for flats — 3 918 €/m² in August 2026 — includes the Paris region at 6 420 €/m², which pulls it up. So we work region by region, and state a floor area rather than just “a flat”.
| Market | Average price | Floor area |
|---|---|---|
| Saint-Étienne | 1 249 €/m² | 120 m² |
| Limoges | 1 579 €/m² | 95 m² |
| Centre-Val de Loire | 1 730 €/m² | 87 m² |
| Hauts-de-France | 1 823 €/m² | 82 m² |
| Normandie | 2 020 €/m² | 74 m² |
| Le Mans | 2 036 €/m² | 74 m² |
| Nouvelle-Aquitaine | 2 066 €/m² | 73 m² |
| Bretagne / Occitanie | ≈ 2 365 €/m² | 64 m² |
| Pays de la Loire | 2 442 €/m² | 62 m² |
| Auvergne-Rhône-Alpes | 2 625 €/m² | 57 m² |
| Nantes / Lille | ≈ 3 368 €/m² | 45 m² |
| Rennes / Strasbourg | ≈ 3 814 €/m² | 39 m² |
Areas calculated on €150,340, that is the French €162,530 less about 7.5% in conveyancing fees on an older property. The page uses75 m², a value that sits in the middle of the table and cannot be accused of having been picked to flatter. In a large city the same sum buys a one-bedroom: the table is there so everyone can place themselves.
The ten milestones shown in the app and on the page are widely published public-health markers, used as they stand and never reworded for impact. None is brought forward in time, none is rounded, and none promises a medical outcome. Cashtray is a counter, not a treatment: to quit, a health professional will always be more use than an app.