Enter when you last smoked and watch two live countdowns: carbon monoxide against WHO’s twelve-hour anchor, and nicotine against seventy-two hours — about thirty-six half-lives at nicotine’s two-hour plasma average. The page names the phase you are in and marks the 48-to-72 hour stretch, which is the one every source agrees is hardest.
Leave blank to use right now as your quit moment
Everything on this page is one subtraction repeated every second: the time now, minus the time you gave for your last cigarette. Both rings are that elapsed figure as a fraction of a fixed window — twelve hours for carbon monoxide, seventy-two for nicotine — capped at 100%. Each ring is a circle of radius 50 with a 314-unit dash, which is its circumference, so the arc drawn is the percentage stated beside it.
Where the two windows come from. Nicotine's plasma half-life after smoking averages about two hours, and cotinine, the metabolite it becomes, about sixteen; those are Benowitz, Hukkanen and Jacob's figures in the standard pharmacology review. Seventy-two hours is roughly thirty-six nicotine half-lives, which is why it is the conventional point at which nicotine and its immediate metabolites are treated as gone. The twelve hours is WHO's anchor for carbon monoxide returning to a non-smoker's level; the CDC says several days and the NHS says forty-eight hours. The ring runs on the earliest of the three, and the page says which one it is rather than letting the reader assume all three agree.
What is ours: the five phase labels and the hours they change at — under eight hours, eight to twelve, twelve to forty-eight, forty-eight to seventy-two, and past seventy-two. Those boundaries are a reading of the two windows above, not a published staging system, and no clinician would recognise them as one. The peak-craving bar spans the same forty-eight-to-seventy-two-hour stretch for the same reason.
Your quit moment is kept in this browser and nowhere else, and the countdown runs off your device clock. Change the clock and the numbers change, because there is no server here holding a second opinion.
Nothing on this page is medically reviewed and nothing above measures anything about you — it explains a calculation. Where a number here is our own judgement rather than a published figure, the note says so and cites nothing; where the health bodies disagree, it carries the disagreement. Method last checked 21 August 2026.
Carbon monoxide from cigarette smoke binds to haemoglobin 200 times more strongly than oxygen, forming carboxyhaemoglobin. This directly reduces your blood's oxygen-carrying capacity — essentially creating mild chronic hypoxia. Carbon monoxide starts leaving your blood as soon as you stop, and the bodies that measure it place the return to a non-smoker's level between twelve hours (WHO) and several days (CDC), with the NHS at 48 hours. The ring above tracks WHO's twelve-hour anchor, which is the earliest of them.
Nicotine has a biological half-life of approximately 2 hours. Its primary metabolite, cotinine, has a half-life of roughly 16 hours. Within 72 hours, nicotine and its immediate metabolites are effectively cleared from the bloodstream. This is why the 48–72 hour window is the hardest: receptors in your brain are maximally starved. After 72 hours, the brain begins downregulating receptor density, and the acute physical pull weakens.
Understanding which phase you are in removes the fear of the unknown. Just Smoked means nicotine is still active. CO Clearing means your blood oxygen is improving. Nicotine Clearing is the hardest phase — peak withdrawal — but it is time-limited. Almost Clear is the final stretch. Cleared means the acute pharmacological chapter is closed.
Nicotine has a half-life of about 2 hours, but its metabolite cotinine lingers for days. Here's exactly how long nicotine stays in your blood, urine, and saliva.
quit · 4 min readHow long nicotine stays in your blood, urine, saliva, and hair — with half-life science explained. Includes cotinine detection windows for drug tests.
science · 5 min readCotinine is what nicotine tests actually detect. Learn what cotinine is, how long it stays in your system, and what levels mean for blood, urine, and saliva tests.
Free nicotine withdrawal timeline. Enter your last cigarette to see which symptoms belong to each phase, when withdrawal peaks, and when it starts easing.
Free craving countdown timer. Nicotine cravings peak and pass in 3–5 minutes; start the timer, follow the 4-7-8 breathing guide, and outlast this one.
Free lung recovery timeline. Enter your quit date to see what your lungs and heart are doing right now, from 20 minutes to 10 years, sourced to NHS and CDC.
A live recovery ring, phase tracking, and a milestone the moment your body passes it.
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