How many hours ahead is IST compared to GMT?

India Standard Time (IST, UTC+5:30) is 5 hours and 30 minutes ahead of GMT (UTC+0) year-round. In summer when the UK switches to BST (UTC+1), IST is only 4 hours and 30 minutes ahead of British local time. India never observes daylight saving time, so any change in the gap is caused by the UK’s clock change.

What is the best time to schedule a call between India and London?

The most comfortable window is afternoon India time / morning UK time. A call at 2:30–4:30 PM IST is 9 AM–11 AM GMT (winter) or 9 AM–11 AM BST (summer, with IST at 1:30–3:30 PM). This catches India after lunch and the UK in a fresh morning slot. Both sides are in comfortable working hours.

Why does IST have a half-hour offset from GMT?

India chose UTC+5:30 to create a single nationwide time zone that splits the difference across the country’s 30-degree longitude span. The half-hour offset minimizes the solar noon deviation for the most populated parts of the country. It is not aligned to any whole-hour UTC zone, which creates the fractional gaps that surprise schedulers.

IST vs GMT: Time Difference and Conversion

March 24, 2026

India Standard Time (IST, UTC+5:30) and Greenwich Mean Time (GMT, UTC+0) differ by 5 hours and 30 minutes — the fractional half-hour being the defining feature of the India-UK scheduling relationship. For the large number of UK companies that outsource or offshore work to India, and for the Indian diaspora in Britain, this IST/GMT gap is a daily reality.

The 5.5-Hour Gap

IST sits at UTC+5:30, placing Mumbai and Delhi 5 hours and 30 minutes ahead of London in winter. When London is at 9 AM GMT, it is 2:30 PM IST in India. When India’s business day ends at 6 PM IST, London is at 12:30 PM GMT — still well within the UK working day. This means there is a surprisingly good overlap window for UK-India calls compared to US-India scheduling.

In summer, the UK moves to BST (UTC+1), narrowing the gap to 4.5 hours. London at 9 AM BST is 1:30 PM IST. This shift makes summer the better period for UK-India collaboration, as 9 AM BST calls catch India at a slightly more comfortable time than 9 AM GMT / 2:30 PM IST.

See the current IST/GMT offset

Add London and Mumbai to your world clock to see both current times and confirm today’s exact gap.

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Quick Conversion Reference

To convert GMT to IST, add 5 hours and 30 minutes. To convert IST to GMT, subtract 5 hours and 30 minutes. When the UK is on BST (summer), add or subtract 4 hours and 30 minutes instead.

GMT (UK winter)	India Standard Time (IST)
6:00 AM GMT	11:30 AM IST
7:00 AM GMT	12:30 PM IST
8:00 AM GMT	1:30 PM IST
9:00 AM GMT	2:30 PM IST
10:00 AM GMT	3:30 PM IST
11:00 AM GMT	4:30 PM IST
12:00 PM GMT	5:30 PM IST
1:00 PM GMT	6:30 PM IST
2:00 PM GMT	7:30 PM IST

Tip

The ideal UK-India meeting window is 9–11 AM GMT (2:30–4:30 PM IST) in winter. London starts its day fresh; India is in a productive post-lunch afternoon. In summer (BST), 9–11 AM BST = 1:30–3:30 PM IST, catching India slightly earlier and often before the afternoon energy dip.

Why the Half-Hour Offset Matters Practically

Most schedulers think in whole hours, which means the 30-minute offset catches people off guard. A meeting at “9 AM UK time” is not 2 PM or 3 PM IST — it is 2:30 PM. A meeting at “5 PM IST” is not 11 AM or 12 PM GMT — it is 11:30 AM. In scheduling tools that display in local time, this half-hour step is handled automatically, but when doing mental arithmetic or communicating times verbally, the 30-minute increment is easy to drop.

Example

A UK project manager sends an invite for “10 AM GMT” to an Indian counterpart. The Indian colleague, doing quick mental math, calculates 10 AM plus 5 hours = 3 PM IST and shows up at 3 PM. The UK PM is waiting since 3:30 PM IST. The 30-minute discrepancy from the half-hour offset caused a missed start. Always let a timezone converter verify the exact IST time rather than doing mental math.

UK-India Business Corridor

The UK has a large and economically significant Indian diaspora, and the India-UK trade and outsourcing relationship is among the world’s largest. British companies with India development centers, BPO operations, or distribution partners have made UK-IST coordination a daily routine. Many UK businesses set their India team standup at 9 AM GMT (2:30 PM IST) and their end-of-day handoff at 4 PM GMT (9:30 PM IST), which is after India’s standard hours but within the late working culture common in Indian IT services.

Note

During the brief UK DST transition windows (late March and late October), the gap between London and India shifts by one hour. If you have standing calls with India, update your calendar invites when UK clocks change. India will not notify you — their clocks never move.

Schedule across the UK-India gap

Use the meeting planner to find the best times for your London and Indian city teams to connect.

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Time Zone ConverterConvert times between IST and GMT/BST, with the half-hour offset calculated correctly.

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Frequently Asked Questions

How many hours ahead is IST compared to GMT?: India Standard Time (IST, UTC+5:30) is 5 hours and 30 minutes ahead of GMT (UTC+0) year-round. In summer when the UK switches to BST (UTC+1), IST is only 4 hours and 30 minutes ahead of British local time. India never observes daylight saving time, so any change in the gap is caused by the UK’s clock change.
What is the best time to schedule a call between India and London?: The most comfortable window is afternoon India time / morning UK time. A call at 2:30–4:30 PM IST is 9 AM–11 AM GMT (winter) or 9 AM–11 AM BST (summer, with IST at 1:30–3:30 PM). This catches India after lunch and the UK in a fresh morning slot. Both sides are in comfortable working hours.
Why does IST have a half-hour offset from GMT?: India chose UTC+5:30 to create a single nationwide time zone that splits the difference across the country’s 30-degree longitude span. The half-hour offset minimizes the solar noon deviation for the most populated parts of the country. It is not aligned to any whole-hour UTC zone, which creates the fractional gaps that surprise schedulers.