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Fasting hours calculator

Work out the length of the fast for any date and place: when it begins at Fajr, when it ends at Maghrib, and how many hours that is.

Place and date

Positive north, negative south

Positive east, negative west

Hours ahead of UTC at that place on that date, daylight saving included

Calculation method

Widely used across Europe and much of the world. A reasonable default if you are unsure.

Show nothing rather than estimate. Ask your local mosque what they follow.

Methods disagree with one another by up to twenty minutes at Fajr and Isha, because they disagree about which angle of twilight marks the boundary. Follow whichever your local mosque follows rather than whichever gives the answer you prefer.

Clock

Length of the fast

Enter a location and date, or tap Use my location, to see when the fast begins and ends.

What the tool measures

The span from the start of Fajr to Maghrib on the date you choose. Fajr is dawn, when the sky first begins to lighten, rather than sunrise, the gap between the two is often an hour and a half, and treating sunrise as the start of the fast is the single most common mistake made with a timetable.

Why two timetables disagree

Maghrib is sunset, and nobody disputes where the sun is. Fajr is defined by how far the sun sits below the horizon at dawn, and organisations settled on different angles for it: 15 degrees, 18, 19.5. That difference is worth up to twenty minutes at the start of the fast, and it is almost always the reason this tool and a printed timetable differ. Set the method your mosque follows.

Long days and short ones

In Britain the fast runs from about ten hours in December to nineteen in June, because dawn and sunset move so far apart across the year. Nearer the equator the length barely changes at all. Both are simply what the sun does at that latitude.

Far enough north there comes a point where dawn never arrives. The sky does not get properly dark before it begins to lighten again. There is then no Fajr to measure from. This tool reports that rather than filling the gap with an estimate, and offers the conventions communities use instead.

A planning aid

These figures are computed from the sun’s position, not published by a mosque. For the actual start and end of a fast, follow your local mosque’s timetable.

Questions

When exactly does the fast begin?
At the start of Fajr, which is dawn, not sunrise. That is typically an hour to an hour and a half before the sun appears, and it is the moment suhoor must end. Using sunrise instead would add that time to your eating window by mistake, which is the most common error people make with a timetable.
Why is the length different from the mosque timetable down the road?
Almost always because of the Fajr angle. Mosques follow different calculation conventions, and the gap between an 18-degree and a 15-degree Fajr can be twenty minutes. Set the method your mosque uses and the numbers should line up.
Why are the hours so long in northern summers?
Because dawn arrives very early and sunset very late. In Britain a Ramadan falling in June means roughly nineteen hours between Fajr and Maghrib, and further north it gets longer still, until the point where dawn never properly arrives at all and the calculation has nothing to measure.
What happens where there is no dawn or no sunset?
The tool says so rather than producing a number. Above roughly 48 degrees of latitude there are dates in summer when the sun never drops to the Fajr angle, and inside the Arctic Circle there are days with no sunset at all. Several conventions exist for those places and communities differ on which to follow, so the choice is offered rather than made for you.
Can I use this to plan Ramadan in advance?
Yes, for the daily hours, put in any future date and it will calculate for it. What it will not tell you is which dates Ramadan falls on, since that depends on the sighting of the moon and is announced locally.
Does it account for altitude?
No. It assumes a sea-level horizon, as published timetables do. Height above sea level brings sunset marginally later and dawn marginally earlier, by a minute or two in most inhabited places.

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