GMT to IST Converter
IST is 5 hours 30 minutes ahead of GMT. During UK BST (summer), the gap narrows to 4 hours 30 minutes.
Daylight saving note: During UK BST (late March–late October), the gap narrows from 5h 30m to 4h 30m. India never observes DST.
GMT/BST to IST Conversion Table
Full 24-hour reference table. Use the live clocks above for the exact current offset.
| 🇬🇧 GMT/BST | 🇮🇳 GMT → ISTUTC+0 to UTC+5:30 | 🇮🇳 BST → ISTUTC+1 to UTC+5:30 | Note |
|---|---|---|---|
| 00:00 | 5:30 AM | 4:30 AM | |
| 01:00 | 6:30 AM | 5:30 AM | |
| 02:00 | 7:30 AM | 6:30 AM | |
| 03:00 | 8:30 AM | 7:30 AM | |
| 04:00 | 9:30 AM | 8:30 AM | |
| 05:00 | 10:30 AM | 9:30 AM | |
| 06:00 | 11:30 AM | 10:30 AM | |
| 07:00 | 12:30 PM | 11:30 AM | |
| 08:00 | 1:30 PM | 12:30 PM | |
| 09:00 | 2:30 PM | 1:30 PM | |
| 10:00 | 3:30 PM | 2:30 PM | |
| 11:00 | 4:30 PM | 3:30 PM | |
| 12:00 | 5:30 PM | 4:30 PM | |
| 13:00 | 6:30 PM | 5:30 PM | |
| 14:00 | 7:30 PM | 6:30 PM | |
| 15:00 | 8:30 PM | 7:30 PM | |
| 16:00 | 9:30 PM | 8:30 PM | |
| 17:00 | 10:30 PM | 9:30 PM | |
| 18:00 | 11:30 PM | 10:30 PM | |
| 19:00 | 12:30 AM | 11:30 PM | next day |
| 20:00 | 1:30 AM | 12:30 AM | next day |
| 21:00 | 2:30 AM | 1:30 AM | next day |
| 22:00 | 3:30 AM | 2:30 AM | next day |
| 23:00 | 4:30 AM | 3:30 AM | next day |
* "next day" = converted time falls on the following calendar day.
Best Hours to Schedule Greenwich Mean Time–India Standard Time Calls
London–India has the most comfortable overlap of any major Western city. London's 9:00 AM GMT = 2:30 PM IST. The full morning in London (9 AM–1:30 PM GMT) aligns with India's afternoon (2:30–7:00 PM IST) — giving both teams a solid half-day to collaborate.
About Greenwich Mean Time (GMT/BST)
Greenwich Mean Time (GMT, UTC+0) is the UK's winter timezone. From late March to late October, the UK switches to BST (British Summer Time, UTC+1), narrowing the gap with India. London is the starting point of the global timezone system — the GMT meridian runs through Greenwich.
About India Standard Time (IST)
India Standard Time (IST, UTC+5:30) sits 5.5 hours ahead of GMT. This is a more workable gap than the US-India difference — UK teams can hold morning calls that land during India's afternoon.
How to Avoid Greenwich Mean Time–India Standard Time Conversion Mistakes
India Standard Time is already on the next calendar day from these GMT/BST times onward: 6:30 PM for GMT → IST, 7:30 PM for BST → IST. For example, 11:00 PM GMT/BST is 4:30 AM in India Standard Time on the next day (GMT → IST).
Abbreviations can be ambiguous here: Greenwich Mean Time switches between GMT and BST across the year, while India Standard Time stays on IST year-round. City names and IANA time zones (Europe/London and Asia/Kolkata) are safer for exact scheduling if you're automating anything, since they resolve the right abbreviation automatically instead of needing a manual seasonal check.
Worked Example: A London Late-Morning Call With India
If you work from London, late morning is the sweet spot for India. An 11:00 AM start in London is 4:30 PM in India while the UK is on GMT, and 3:30 PM once the UK is on BST. A 1:00 PM start is 6:30 PM on GMT and 5:30 PM on BST.
Work backward from India's 5:00 PM and you get the latest London start. That's 11:30 AM on GMT and 12:30 PM on BST. A call that begins at noon in London is fine in either season, but one at 1:00 PM only works if India is happy to start after 6:00 PM in winter.
India doesn't change its clocks, so every change comes from the UK side. In the week of the last Sunday in March, a London call stays at the same London time and moves an hour earlier on India's clock. Mention the change in the invite so the India team doesn't get surprised.
Frequently Asked Questions
What is the GMT to IST time difference?
IST is 5 hours 30 minutes ahead of GMT. During UK BST (late March–late October), the gap is 4 hours 30 minutes. India does not change its clocks.
What time is 9 AM GMT in IST?
9:00 AM GMT is 2:30 PM IST. During UK BST, 9:00 AM BST is 1:30 PM IST. The half-hour component of IST (UTC+5:30) always adds :30 to any round-hour GMT time.
Why does India have a half-hour timezone offset?
India set UTC+5:30 in 1905 to create a single timezone for the whole subcontinent. The longitude of India's geographic centre falls at ~82.5°E, corresponding to UTC+5:30. This half-hour offset has remained since.
What is the best time for a UK-India call?
The best window is 9:00 AM–1:30 PM GMT (2:30–7:00 PM IST). This gives London a full morning and India a comfortable afternoon. After 1:30 PM London, India starts entering evening hours.