What is the GMT to IST Converter?
India Standard Time (IST) is the time zone used across all of India. It is fixed at 5 hours and 30 minutes ahead of Greenwich Mean Time (GMT/UTC), with no daylight saving adjustments throughout the year. This converter takes any GMT clock time and instantly returns the equivalent IST, including whether the conversion rolls over into the next day.
How to use it
Enter the GMT hour (0–23) and minute (0–59), then read the result. The hero box shows the IST time in 24-hour HH:MM format, and the table tells you the day offset — useful when an evening GMT time becomes early morning of the following day in India.
The formula explained
The core rule is simply IST = GMT + 5.5 hours. To handle minutes cleanly, the calculator converts the GMT time to total minutes, adds 330 (\(5 \times 60 + 30\)), then takes the result modulo 1440 (the number of minutes in a day). If the sum reaches or exceeds 1440, the IST falls on the next day.
$$\text{IST} = \left(\,\text{GMT Hour} \times 60 + \text{GMT Minute} + 330\,\right) \bmod 1440$$
Worked example
Suppose it is 20:00 GMT. In minutes that is \(20 \times 60 = 1200\). Add 330 to get 1530. Since \(1530 \geq 1440\), the result wraps: \(1530 - 1440 = 90\) minutes = 01:30. So 20:00 GMT equals 01:30 IST the next day.
$$\text{IST}_{\min} = \left(\,20 \times 60 + 0 + 330\,\right) \bmod 1440 = 1530 \bmod 1440 = 90$$
FAQ
Is IST the same as UTC+5:30? Yes. GMT and UTC are effectively identical for everyday time conversion, so IST is UTC+5:30.
Does India observe daylight saving time? No. India does not use DST, so the +5:30 offset is constant all year.
What does "next day" mean in the result? When adding 5:30 pushes the time past midnight, the IST date moves to the following calendar day relative to the GMT date you entered.
