5:2 and alternate-day fasting planner
5:2 means two low-calorie fast days a week, 4:3 means three, and alternate-day fasting means a fast day every other day. Pick yours, choose your fast days, and see the next four weeks with every fast day marked. One click adds them to your calendar.
Your plan
The 500 and 600 calorie fast-day figures are a popular convention, roughly a quarter of what most people usually eat, not an official limit. On the other days, eat normally rather than making up for the fast day. If you take medicine for diabetes or blood pressure, talk to your doctor before your first fast day.
How to use the 5:2 and alternate-day planner
Choose 5:2, 4:3 or alternate day, then your sex at birth and a start date. The start date begins as today. For 5:2 and 4:3, tick the weekdays you want as fast days. The planner starts you on Monday and Thursday for 5:2, and on Monday, Wednesday and Friday for 4:3.
The plan box shows your fast days, a calorie figure for each one and how many fall in the next four weeks. Below that, each of the 28 days is listed as “Fast day” or “Normal”. The calendar button downloads a standard .ics file with one all-day event for each fast day. Each event is titled “Fast day (5:2)”, or 4:3 or ADF, with the calorie figure in its note.
How the planner places your fast days
For a 5:2 intermittent fasting plan or a 4:3 plan, your fast days repeat on the same weekdays every week. Tick too many or too few and the planner asks you to pick exactly 2 (for 5:2) or 3 (for 4:3). For 5:2 it also warns when your two days sit side by side, and that includes Sunday followed by Monday.
The 4:3 plan has no back-to-back warning, so spacing the days is up to you. The default of Monday, Wednesday and Friday keeps a normal day after each one. In a 12-month trial of 165 adults, 4:3 fast days were 3 non-consecutive days a week with 80% less food. That group lost about 2.9 kg more than people who cut calories every day by the same weekly amount.
For alternate-day fasting, the weekday boxes disappear. Your start date is a fast day, then every other day after it. Seven is an odd number, so the fast days drift through the week instead of landing on fixed weekdays.
Worked example: four weeks from Monday 2 November 2026
These are the planner’s own results with a start date of Monday 2 November 2026 and the default days.
| Method | Fast days | Fast days in 4 weeks | Week 1 | Week 2 |
|---|---|---|---|---|
| 5:2 | Monday and Thursday | 8 | Mon 2, Thu 5 Nov | Mon 9, Thu 12 Nov |
| 4:3 | Monday, Wednesday and Friday | 12 | Mon 2, Wed 4, Fri 6 Nov | Mon 9, Wed 11, Fri 13 Nov |
| Alternate day | Every other day from the start | 14 | Mon 2, Wed 4, Fri 6, Sun 8 Nov | Tue 10, Thu 12, Sat 14 Nov |
Weeks 3 and 4 repeat the same pattern. For a woman, each fast day shows about 500 kcal. For a man, it shows about 600 kcal.
What the 500 and 600 calorie figures mean
The planner gives one fast-day number for each sex, whatever your weight, height or activity. Both numbers come from common 5:2 practice, at about a quarter of a usual day’s food, and no official limit stands behind them. The main 5:2 trial gave 107 women about 2,710 kJ (about 650 kcal) on each of two fast days a week. Over 6 months they lost the same weight as women who cut calories every day.
On the other days, eat as you normally would. A very large meal the day after a fast day cancels part of the week’s saving. To find what a normal day is for your body, use the TDEE calculator.
Who should check with a doctor first
Anyone on blood-pressure tablets or diabetes medicine needs a doctor’s advice before the first fast day in the plan. On insulin or a sulfonylurea, a low-calorie day raises the chance of blood sugar dropping too low. Pregnancy, breastfeeding and being under 18 are reasons to get that advice first as well. Where body weight is low, or after an eating disorder, we advise leaving fast days out of the plan. If fast days leave you bingeing or anxious about food, stop and speak to a doctor.
Related tools and guides
The full guide to fast-day methods sets out what the trials found for each method and the weekly calorie sums. If a daily eating window suits you better than fast days, the schedule chooser suggests one from the times you like to eat. The weekly calorie total counts for more than the pattern, and the evidence on fasting and weight shows why.
Frequently asked
What is a 5:2 intermittent fasting plan?
A 5:2 plan gives you two low-calorie fast days a week, always on the same weekdays, and five days of normal eating. The planner starts you on Monday and Thursday, and you can move them to any two days. It then lists the next four weeks, which holds 8 fast days.
How many calories are allowed on a 5:2 fast day?
The planner shows about 500 kcal a fast day if you choose female, and about 600 if you choose male. No health body sets these numbers. They come from common 5:2 practice, at about a quarter of a usual day's food. Women in the main 5:2 trial had about 650 kcal on each fast day.
What is a 4:3 intermittent fasting plan?
A 4:3 plan has three low-calorie fast days and four ordinary days each week. The planner suggests Monday, Wednesday and Friday, so each fast day has a normal day after it. A year-long trial of 4:3 also kept the three fast days apart.
Can I do my 5:2 fast days at the weekend?
Yes. Tick Saturday and Sunday and the planner will build the plan, but it will warn you that the two days are back to back. It suggests a normal day in between, which also lets you eat properly before the second fast day.
How does the planner set out alternate-day fasting?
Your start date is the first fast day, and every second day after it is another. Over four weeks that makes 14 fast days. Because a week has an odd number of days, you get 4 fast days one week and 3 the next.