Convert GMT to IST

India Standard Time is 5 hours 30 minutes ahead of GMT. When it's 12:00 PM (noon) GMT, it's 5:30 PM IST. India has no daylight saving, so the offset from GMT is fixed all year.

GMT to IST at a glance

GMTIndia (IST)
6:00 AM11:30 AM
8:00 AM1:30 PM
9:00 AM2:30 PM
12:00 PM (noon)5:30 PM
3:00 PM8:30 PM
5:00 PM10:30 PM
6:00 PM11:30 PM
9:00 PM2:30 AM (next day)
12:00 AM (midnight)5:30 AM (next day)

To convert GMT to IST, add 5 hours 30 minutes. To go the other way (IST to GMT), subtract 5 hours 30 minutes.

Convert any time instantly

The half-hour offset trips up tools that only handle whole hours. The ZoneKit Time Zone Converter handles it natively — set your source (London for GMT, Mumbai or New Delhi for IST) and it shows the exact equivalent, half hour and all, with a day-rollover label when the time crosses midnight.

GMT vs London time — an important distinction

GMT (Greenwich Mean Time) is a fixed reference that never changes. London uses GMT in winter, but from late March to late October it switches to British Summer Time (BST, GMT+1). So:

  • GMT to IST is always +5 hours 30 minutes.
  • London to India is +5:30 in winter (when London is on GMT) but +4:30 in summer (when London is on BST).

If you're coordinating with someone in London specifically, check whether it's BST season. If you're working from a fixed GMT reference — common in aviation, shipping schedules, and international broadcasts — it's a clean +5:30 year-round.

Why India is half an hour off

India runs on a single national time zone of UTC+5:30. The half hour exists because India is wide enough east-to-west to span nearly two whole time zones — so a half-hour offset splits the difference and lets the entire country share one clock. India standardised on UTC+5:30 in 1955. It's shared by around 1.4 billion people, making it the most populous single time offset on Earth. Nepal goes one step further with UTC+5:45, a 45-minute offset.

Frequently asked questions

How many hours is IST ahead of GMT?

India Standard Time is 5 hours and 30 minutes ahead of GMT. When it is 12:00 PM (noon) GMT, it is 5:30 PM IST. India does not observe daylight saving, so this offset is fixed year-round.

What is 12 PM GMT in IST?

12:00 PM (noon) GMT is 5:30 PM IST. Add 5 hours and 30 minutes to any GMT time to get the India equivalent.

Is the difference between London and India always 5.5 hours?

Only in winter. GMT-to-IST is always 5:30, but London switches to British Summer Time (GMT+1) from late March to late October. During UK summer, London is 4:30 behind India, not 5:30.

Why is India half an hour off from whole-hour time zones?

India uses a single national time zone of UTC+5:30, a half-hour offset chosen so one clock could serve a country that spans almost two whole time zones. India adopted UTC+5:30 nationally in 1955.

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