How many hours do Muslims fast in the UK?

It depends on the year. In the UK a fast lasts roughly 9 to 10 hours in midwinter and 18 hours or more in midsummer, because Ramadan moves about 10 to 11 days earlier every year. In the mid-2020s Ramadan falls in February and March, so most fasts are around 11 to 14 hours.

Why the length keeps changing

Ramadan follows the Islamic lunar calendar, which is about 11 days shorter than the solar year. So the month slides earlier through the seasons and takes roughly 33 years to pass through all of them. A fast always runs from dawn (Fajr) to sunset (Maghrib), so the number of hours depends on the season you get:

Winter Ramadan: about 9 to 10 hours in December, with a very late dawn and an early sunset.
Spring or autumn Ramadan: about 12 to 14 hours.
Summer Ramadan: around 18 hours or more in the south of England, and longer in Scotland. The last run of summer Ramadans in the UK was in the mid-2010s.

These figures are approximate. Your local mosque timetable gives the exact start and end for your town.

What the Quran says about the limits

The beginning and end of the fast are set by the sky, wherever you live:

وَكُلُوا۟ وَٱشْرَبُوا۟ حَتَّىٰ يَتَبَيَّنَ لَكُمُ ٱلْخَيْطُ ٱلْأَبْيَضُ مِنَ ٱلْخَيْطِ ٱلْأَسْوَدِ مِنَ ٱلْفَجْرِ ۖ ثُمَّ أَتِمُّوا۟ ٱلصِّيَامَ إِلَى ٱلَّيْلِ "[You may] eat and drink until you see the light of dawn breaking the darkness of night, then complete the fast until nightfall." Quran 2:187

In a British summer the sky never gets fully dark, so pinpointing Fajr is hard. Most UK mosques solve this by following one published timetable that uses an agreed method for the dawn. The same question comes up in Scandinavia, where it is even more extreme. See How do Muslims fast in a Nordic summer?

Elsewhere in Europe

Further south, in Spain or Italy, summer fasts are shorter than in Britain, roughly 16 to 17 hours. Further north they are longer, and in the far north of Scandinavia they can pass 20 hours. Winter fasts are short everywhere, so many Muslims enjoy those years as a gentle start.

If a long fast is too hard

Allah gives clear ease to people who struggle:

Illness or travel: if fasting would genuinely harm your health, or you are travelling, you may skip days and make them up later, ideally in the short days of winter (Quran 2:185).
Long days alone: for a healthy adult, long hours are not by themselves an excuse to skip. Speak to your local imam if you are unsure about your own situation.

Days you miss can be made up later. See Do I have to make up missed Ramadan fasts? For help finding the right clock times, see What time do I start and stop fasting in Ramadan?

Getting through a long day

Eat a slow, filling suhoor, such as oats, eggs, yoghurt and fruit.
Drink water steadily between iftar and bed rather than all at once.
Take a short afternoon nap if you can, and save heavy tasks for the morning.

Key points

UK fasts range from about 9 to 10 hours in winter to 18 hours or more in summer.
Ramadan moves 10 to 11 days earlier each year and cycles through all seasons in about 33 years.
Follow your local mosque timetable for exact dawn and sunset times.
Illness and travel are valid reasons to make up days later.

Tip: Save your mosque's Ramadan timetable to your phone before the month starts, and set an alarm 15 minutes before Fajr so suhoor never catches you out.