Ramadan Fasting Hours Calculator
Calculate fasting hours from dawn to sunset for any location and date during Ramadan. Enter values for instant results with step-by-step formulas.
Reviewed for accuracy by Daniel Agrici, Founder & Lead Developer
Ramadan Fasting Hours Calculator
Calculator
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Formula: Fasting Hours = Maghrib Time - Fajr Time
Worked example — Fasting hours: approximately 14 hours | Fajr: ~4:15 AM | Maghrib: ~6:15 PM
Formula
Fasting Hours = Maghrib Time - Fajr Time
Where Fajr is calculated as the time when the sun is 15 to 19 degrees below the horizon (depending on method) before sunrise, and Maghrib is the time of sunset. The solar hour angle formula uses latitude, solar declination, and the relevant twilight angle to determine exact times.
Worked Examples
Example 1: Fasting Hours in Kabul (Mid-Ramadan 2025)
Problem:Calculate fasting hours for Kabul, Afghanistan (latitude 33.9 N) on the 15th day of Ramadan 2025 using the standard 18-degree method.
Solution:Solar declination for day 73 of year: approximately 3.5 degrees Fajr (18 degrees below horizon): approximately 4:15 AM Maghrib (sunset): approximately 6:15 PM Fasting duration: 6:15 PM - 4:15 AM = 14 hours 0 minutes Daylight hours (sunrise to sunset): approximately 12h 10m
Result:Fasting hours: approximately 14 hours | Fajr: ~4:15 AM | Maghrib: ~6:15 PM
Example 2: Comparison: Makkah vs London (Summer Ramadan)
Problem:Compare fasting hours between Makkah (21.4 N) and London (51.5 N) when Ramadan falls in late June.
Solution:Makkah (21.4 N, summer solstice area): Solar declination: ~23.4 degrees Fasting duration: approximately 15 hours London (51.5 N, near summer solstice): Solar declination: ~23.4 degrees Fasting duration: approximately 18-19 hours Difference: London fasts 3-4 hours longer due to higher latitude
Result:Makkah: ~15 hours | London: ~18-19 hours | Difference: ~3-4 hours longer in London
Frequently Asked Questions
How are Ramadan fasting hours calculated from a scientific perspective?
Ramadan fasting hours are calculated using astronomical formulas based on the position of the sun relative to a specific location on Earth. The fasting period begins at Fajr (true dawn), when the sun is approximately 18 degrees below the horizon before sunrise, and ends at Maghrib (sunset), when the sun dips below the horizon. The calculation requires knowing the geographic latitude and longitude of the location, the day of the year (which determines solar declination), and the chosen calculation method for Fajr angle. The solar declination changes throughout the year as the Earth orbits the sun with its tilted axis, which is why fasting hours vary dramatically between summer and winter Ramadan and between different latitudes. Locations closer to the equator experience relatively consistent fasting hours year-round.
Why do fasting hours vary so much between different countries?
The variation in fasting hours between countries is primarily driven by differences in geographic latitude, which determines how long the sun takes to travel across the sky. Countries near the equator, such as Indonesia, Malaysia, and equatorial African nations, experience relatively consistent fasting hours of approximately 12 to 13 hours regardless of when Ramadan falls in the Gregorian calendar. Countries at higher latitudes experience extreme variations depending on the season. When Ramadan falls in summer, Scandinavian countries can experience fasting periods of 20 to 22 hours, while the same countries might fast only 8 to 10 hours during a winter Ramadan. This latitude effect also explains why cities like Makkah and Medina, located near the Tropic of Cancer, have moderate fasting hours typically ranging from 13 to 15 hours throughout the year.
What are the different calculation methods for Fajr time?
Several recognized Islamic astronomical organizations have established different angles for calculating Fajr (true dawn) time, leading to variations of 15 to 45 minutes between methods. The Muslim World League (MWL) uses 18 degrees below the horizon for Fajr, which is also the most traditional approach matching classical astronomical definitions of twilight. The Islamic Society of North America (ISNA) uses 15 degrees, producing a later Fajr time and shorter fasting period. The Egyptian General Authority of Survey uses 19.5 degrees, giving the earliest Fajr and longest fasting period. The University of Islamic Sciences, Karachi uses 18 degrees for Fajr. The Umm al-Qura method used in Saudi Arabia employs a fixed 90-minute interval before sunrise for Fajr. Each method has scholarly backing, and Muslims typically follow the method used by their local mosque or Islamic authority.
How should Muslims fast in extreme northern or southern latitudes?
Muslims living at extreme latitudes where the sun may not fully set or rise during summer months face unique challenges that Islamic scholars have addressed through several approaches. The most commonly cited scholarly ruling allows Muslims in these regions to follow the prayer and fasting times of the nearest city with distinguishable dawn and sunset. Another approach permits following the times of Makkah or Medina as the holiest cities in Islam. A third opinion suggests dividing the 24-hour period into equal proportional segments based on the last day when normal sunrise and sunset were observable. The European Council for Fatwa and Research has recommended that in areas above 48 degrees latitude where twilight persists, Muslims should follow the nearest city with normal day-night cycles. Many mosques in Scandinavian countries, northern Canada, and Alaska publish adjusted schedules each Ramadan based on their chosen scholarly methodology.
How does the Islamic calendar cause Ramadan to shift each year?
The Islamic (Hijri) calendar is a purely lunar calendar consisting of 12 lunar months that total approximately 354 days, which is about 11 days shorter than the 365-day Gregorian solar calendar. This means Ramadan begins approximately 11 days earlier each Gregorian year, cycling through all seasons over a period of roughly 33 years. A Muslim born in a year when Ramadan falls in summer will experience Ramadan in every season throughout their lifetime, ensuring equitable distribution of longer and shorter fasting days across different regions. This lunar cycle has significant practical implications: Muslims in northern latitudes will experience both the challenge of 18-hour summer fasts and the ease of 8-hour winter fasts, while equatorial Muslims fast consistently similar hours regardless of the seasonal position of Ramadan.
What is the significance of Suhoor timing and how is it calculated?
Suhoor is the pre-dawn meal eaten before the Fajr prayer and the beginning of the daily fast, and its timing is crucial for both the spiritual validity of the fast and physical well-being during the fasting day. Islamically, suhoor should be eaten as close to Fajr as possible while ensuring completion before the adhan (call to prayer). The Prophet Muhammad (peace be upon him) encouraged delaying suhoor, and scholars generally recommend finishing the meal 10 to 15 minutes before Fajr begins as a precautionary measure. The recommended suhoor stop time is calculated by taking the Fajr time and subtracting this safety margin. Nutritionally, the timing matters because eating closer to Fajr minimizes the gap between the last food intake and the beginning of the fast, reducing the total duration of true food deprivation.
How accurate are online fasting time calculators compared to local observations?
Online fasting time calculators use mathematical formulas and astronomical data that are generally accurate to within 1 to 3 minutes for most locations, but several factors can affect real-world accuracy. The calculations assume a flat horizon without obstructions, so mountainous terrain, tall buildings, or valleys can cause actual sunrise and sunset times to differ by several minutes from calculated times. Atmospheric refraction, which bends light and allows the sun to be visible even after it has geometrically set, is accounted for in standard calculations but varies with temperature, humidity, and air pressure. Cloud cover and haze can also affect the visual observation of dawn and sunset. For this reason, most Islamic scholars recommend adding a precautionary buffer of 2 to 5 minutes before the calculated Fajr time and after the calculated Maghrib time.
What is the shortest and longest possible fasting period during Ramadan?
The shortest and longest fasting periods during Ramadan depend on the latitude and the time of year when Ramadan falls. At the equator, fasting hours remain relatively constant at approximately 12 hours and 30 minutes to 13 hours throughout the year, making equatorial regions the most consistent for fasting duration. The shortest fasts experienced by major Muslim populations occur when Ramadan falls in winter at moderate latitudes, with cities like Istanbul, London, and New York experiencing fasting periods as short as 8 to 10 hours. The longest regular fasts occur when Ramadan falls in summer at high latitudes, with cities like Stockholm, Oslo, and Reykjavik potentially reaching 20 to 22 hours of fasting. In truly extreme cases above the Arctic Circle during summer, the sun may not set at all, necessitating alternative scholarly methods for determining fasting times.
How do time zones affect Ramadan fasting calculations?
Time zones affect the display of fasting times but do not change the actual fasting duration, which is determined purely by the sun position relative to the observer location. Solar noon (when the sun is at its highest point) occurs at different clock times depending on where within a time zone a location sits. A city on the eastern edge of a time zone may experience solar noon at 11:30 AM local time, while a city on the western edge of the same zone may have solar noon at 12:30 PM. This means that two cities in the same time zone can have significantly different fasting start and end times on the clock, even if their latitudes are similar. Daylight saving time adds another layer of complexity, shifting clock times by one hour without changing the actual solar position.
What health considerations should be taken into account based on fasting duration?
The duration of daily fasting has direct implications for health management and nutritional planning during Ramadan. For fasts exceeding 16 hours, medical professionals recommend paying particular attention to hydration during non-fasting hours, consuming slow-release carbohydrates and protein at suhoor, and avoiding excessive physical exertion during peak heat hours. People with diabetes, pregnant women, nursing mothers, and those on regular medications should consult healthcare providers before fasting, especially during long summer fasts. Research has shown that the body adapts to the fasting pattern within the first week, with blood glucose levels stabilizing and the body becoming more efficient at utilizing stored energy. Shorter fasts of 10 to 12 hours are generally well-tolerated by healthy adults with minimal health considerations beyond adequate hydration.
References
Reviewed for accuracy by Daniel Agrici, Founder & Lead Developer · Editorial policy
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