How we calculate our numbers

Every number our tools show comes from the formulas on this page. Where a figure comes from research or official guidance, it's linked to its source.

Taper planner

The taper planner and the calculator on our homepage use the same code. The CutPuff app builds plans the same way too, and a shared set of test cases checks that the website and the app agree.

Daily limits

Your plan has a starting count (the puffs you take a day now) and a number of weeks.
In week n of a w-week plan, counting the first week as week 0, the daily limit is starting count × (1 − n ÷ w).
Each limit is rounded to the nearest whole puff, with halves rounded up. For example, in a plan of 8 weeks from 450 puffs, week 6 works out at 112.5, so the limit is 113.
So the first week's limit is your starting count, and the limit steps down by the same amount each week until it reaches 0 on your quit date.

Dates

Your quit date is today + weeks × 7 days. Today is day 0, and each week is 7 days, so day d belongs to week ⌊d ÷ 7⌋.
From the quit date on, the daily limit is 0.
Dates are counted in whole calendar days, so a clock change for daylight saving never moves a date.

Puffs avoided and money saved

Puffs avoided over 90 days is the sum, over days 0 to 89, of starting count − that day's limit. Over a year, it's the same sum over days 0 to 364.
Cost per puff is your weekly spend ÷ (starting count × 7). Money saved over a year is puffs avoided over a year × cost per puff.
Money is only rounded for display: to the cent on the planner, and to whole amounts from 100 up on the homepage.

The projections assume you follow the plan exactly. They count every day from your quit date on as a full day of your starting count saved, and they assume you stop buying at your old rate. Real days rarely match a plan exactly, so treat them as a guide, not a promise. The NHS describes cutting down gradually as one way to make quitting vaping easier, alongside quitting in one step [1].

Nicotine calculator

The formulas

A strength in % becomes mg/ml by multiplying by 10, so 5% is 50 mg/ml.
Nicotine per device = liquid (ml) × strength (mg/ml), rounded to the nearest whole mg.
Nicotine per day = nicotine per device (as rounded) ÷ the days one device lasts you, rounded to the nearest whole mg.
Cigarette comparison = nicotine per day (as rounded) ÷ 10, rounded to the nearest whole cigarette.
Under 1, we show "less than 1 cigarette". At 20 or more, we also show packs of 20: cigarettes ÷ 20 to one decimal place, without a trailing ".0".
With a strength of 0, we show "No nicotine in this liquid" instead of a comparison.

For example, 20 ml at 5% lasting 4 days: 1,000mg per device, 250mg a day, 25 cigarettes, and 1.25 packs, shown as 1.3.

Why 10mg per cigarette

The comparison is with the nicotine in a cigarette's tobacco. Published figures vary: the UK Committee on Toxicity gives an average of 8 to 9mg for a cigarette, and 10 to 15mg for a conventional cigarette [2]. We use 10mg, a round figure within that range.

Content isn't what you absorb

A smoker takes in far less nicotine than a cigarette contains: about 1mg per cigarette. Studies measured an average of 1.04mg [4], and about 1mg with a range of 0.37 to 1.60mg [3]. The Committee on Toxicity gives a typical figure of around 1mg, ranging from about 0.3 to 3.2mg [2].

How much nicotine you absorb from a vape varies much more. It depends on the liquid's strength, your device and how you puff: longer puffs deliver more nicotine [6], and delivery varies widely between people, even on the same device [7] [8]. That's why the calculator compares nicotine content only and doesn't estimate what you absorb.

% and mg/ml

Strength limits are set in mg/ml. In Australia, for example, vapes a pharmacist can supply without a prescription are limited to 20 mg/mL, and therapeutic vapes to 50 mg/mL [9] [10]. Some labels give a percentage instead, and percentages are reported inconsistently: researchers found one liquid described as 5% by weight but 5.9% by volume [5]. Our conversion (% × 10) assumes the % is by volume.

Label accuracy

We take the strength you enter as correct, but labels aren't always accurate. Some e-cigarettes marketed as containing no nicotine have been found to contain it [11].

What these numbers can't tell you

How much nicotine your body absorbs, or how dependent you are.
Anything about your health or risk. These tools aren't medical advice.
Whether cutting down or stopping at once will work better for you. The evidence is mixed, so a doctor, pharmacist or local quit service is the best place to talk it through.
What will actually happen. The planner's projections assume you follow the plan exactly.

Sources

Last reviewed 9 October 2026. Spotted a mistake? Tell us, and we'll correct it and update this date.