The short answer: India (IST, UTC+5:30) is 5.5 hours ahead of GMT (UTC+0). So 12:00 noon GMT is 5:30 PM IST. The two countries share a large working day: a UK morning is an India afternoon, so 9 AM to 12 noon GMT (2:30 PM to 5:30 PM IST) is a comfortable overlap. In UK summer the gap narrows to 4.5 hours, because India never changes its clocks.
The UK and India sit close enough that a single phone call rarely catches anyone asleep. India is only half a day's worth out of step, so your morning to mid-afternoon is India's afternoon to early evening — a wide, reliable shared window all year round.
How far ahead is IST of GMT?
India keeps a single time zone, India Standard Time, at UTC+5:30, and it does not change for daylight saving. The UK sits on GMT (UTC+0) in winter and switches to British Summer Time (BST, UTC+1) from late March to late October, so the gap shifts by an hour with the season.
| UK clock | UK offset | India is ahead by |
|---|---|---|
| GMT (winter) | UTC+0 | 5.5 hours |
| BST (summer) | UTC+1 | 4.5 hours |
GMT to IST conversions
To go from GMT to IST, add 5 hours 30 minutes. Here are the everyday conversions through a working day.
| Time in the UK (GMT) | Time in India (IST) |
|---|---|
| 9:00 AM | 2:30 PM |
| 12:00 noon | 5:30 PM |
| 3:00 PM | 8:30 PM |
| 5:00 PM | 10:30 PM |
These use GMT (UK winter). In UK summer (BST), the same UK clock reading is one hour later than GMT, so India is only 4.5 hours ahead: 12 noon UK time becomes 4:30 PM IST.
The best window for a UK–India call
Because the gap is small, the shared working day is generous. A UK morning lands squarely in the Indian afternoon, so the cleanest overlap is roughly 9 AM to 12 noon GMT, which is 2:30 PM to 5:30 PM IST — comfortably inside business hours on both sides. Push later and you reach the end of the Indian workday: 1 PM GMT is 6:30 PM IST.
India never changes its clocks, but the UK springs forward in late March and falls back in late October, so the gap moves between 5.5 and 4.5 hours. A recurring call set in winter will land an hour off in summer unless you adjust it. For more on the offset, see what is IST.
Stop checking this every time
If you work with India regularly, doing this 5.5-hour arithmetic by hand gets old fast, and the British Summer Time switch is exactly where mistakes creep in. Atlas keeps London and your Indian city side by side in your Mac menu bar, shades the hours when both sides are at their desks, and books any meeting to your calendar in both local times. One glance tells you whether now is a good time to call. For the best calling hours specifically, see our guide to the best time to call India from the UK.
Frequently asked
How many hours ahead is IST of GMT?
What is 12 noon GMT in IST?
Does India observe daylight saving time?
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