Convert GMT to IST
To convert GMT to IST: 12:00 PM GMT is 5:30 PM IST. GMT is UTC+00:00 and IST is UTC+05:30, so IST is 5 hours 30 minutes ahead of GMT, but not all year, as explained below.
In India Standard Time
- On a 24-hour clock
- 12:00 GMT is 17:30 IST
- The offsets
- GMT is UTC+00:00, IST is UTC+05:30
- Difference
- IST is 5 hours 30 minutes ahead of GMT
- Date
- Same calendar day.
- This gap does NOT hold all year Convert through the offset in force on the date you care about.
- The two ends switch on different dates, or one does not switch at all.
- GMT is only in force part of the year European Union and United Kingdom: daylight time starts the last Sunday in March, at 01:00 UTC and ends the last Sunday in October, at 01:00 UTC (Directive 2000/84/EC). In 2026 that is 2026-03-29 to 2026-10-25. London and Dublin in winter is on BST between those dates.
- otherwise BST, UTC+01:00
- Military time zone letters Z (Zulu) is UTC. A to M run east of Greenwich an hour apart, N to Y west, and J is left out. A letter names an offset, so a zone that switches to daylight time changes letter: EST is R, EDT is Q.
- GMT is Z (Zulu), IST is E* (Echo, starred: off the whole hour)
- In Zulu notation Four digits on a 24-hour clock, no colon, then Z for UTC.
- 1200Z
- In every zone
- HST 02:00 AKST 03:00 PST 04:00 AKDT 04:00 MST 05:00 PDT 05:00 CST 06:00 MDT 06:00 EST 07:00 CDT 07:00 EDT 08:00 UTC 12:00 GMT 12:00 BST 13:00 CET 13:00 CEST 14:00 EET 14:00 EEST 15:00 MSK 15:00 IST 17:30 SGT 20:00 HKT 20:00 JST 21:00 AEST 22:00 AEDT 23:00 NZST 00:00 NZDT 01:00
How the Time Zone Converter works
Greenwich Mean Time (GMT) is UTC+00:00 and India Standard Time (IST) is UTC+05:30, so converting GMT to IST means adding 5 hours 30 minutes to the GMT time. IST is 5 hours 30 minutes ahead of GMT.
Worked through: 12:00 PM GMT is 5:30 PM IST.
The gap between these two is not the same all year, which is the thing to get right. IST never shifts and GMT does, so the difference moves. Convert through the offset in force on the date you care about rather than through the abbreviation somebody typed; the offsets above are definitions and the abbreviation is a claim about the calendar.
Five and a half hours forward, and the cleanest India conversion of the three here, because for the five months London is actually on GMT neither end is doing anything seasonal. The catch is the other seven months: London is on BST from late March to late October, when the gap narrows to four and a half hours. Half of the demand for 'GMT to IST' is really 'London to India', and those are two different questions for most of the year.
One thing worth stating plainly, because it is the most common mistake in this whole subject: an abbreviation is not a place. GMT is Greenwich Mean Time, which London and Dublin in winter uses only part of the year; the rest of the time it is on BST at UTC+01:00. IST does not shift. If what you have is a city and a date rather than a pair of abbreviations, that is a different question and needs the tz database, not arithmetic.
Common times for this pair:
- 9:00 AM GMT is 2:30 PM IST - 12:00 PM GMT is 5:30 PM IST - 2:00 PM GMT is 7:30 PM IST - 5:00 PM GMT is 10:30 PM IST
Time Zone Converter FAQ
What is the time difference between GMT and IST?
IST is 5 hours 30 minutes ahead of GMT. GMT is UTC+00:00 and IST is UTC+05:30, and both offsets are definitions rather than measurements, so the subtraction is exact.
What time is 12:00 PM GMT in IST?
12:00 PM GMT is 5:30 PM IST. Add 5 hours 30 minutes and carry the date if it crosses midnight.
Does the difference between GMT and IST change with daylight saving?
Yes, and this is the main thing to watch on this pair. IST is fixed and GMT shifts by an hour for part of the year, so the difference takes more than one value across the year. In 2026 the European Union and United Kingdom switch runs from 2026-03-29 to 2026-10-25.
Is there anything specific to this pair worth knowing?
Five and a half hours forward, and the cleanest India conversion of the three here, because for the five months London is actually on GMT neither end is doing anything seasonal. The catch is the other seven months: London is on BST from late March to late October, when the gap narrows to four and a half hours. Half of the demand for 'GMT to IST' is really 'London to India', and those are two different questions for most of the year.
Someone wrote GMT but it is summer. What do they mean?
Almost certainly the zone rather than the abbreviation: London and Dublin in winter time, which in summer is BST at UTC+01:00 rather than GMT at UTC+00:00. People type the standard-time abbreviation all year round. If an invitation is an hour out from what you calculated, this is why.
More from the Time Zone Converter
- IST to PST
- PST to IST
- EST to IST
- IST to EST
- IST to UTC
- UTC to IST
- Eastern Time to GMT (ET to GMT)
- PST to GMT