IST to London
-4h 30mIST
ISTSOURCELondon
BSTGreen rows indicate typical business hours (9 AM - 5 PM)
IST and BST on the World Map
The map below highlights the IST (India Standard Time) and BST (Greenwich Mean Time) timezone regions across the globe.
IST – India Standard Time
UTC+05:30India Standard Time (IST) is the time zone for India and Sri Lanka, 5 hours and 30 minutes ahead of UTC.
- •India is 10 hours 30 minutes ahead of EST and 5 hours 30 minutes ahead of GMT.
- •India uses a single time zone despite spanning 30° of longitude.
- •IST is one of only a handful of time zones with a 30-minute offset.
- •IST is the most populous single time zone in the world with over 1.4 billion people.
- •The Bombay Stock Exchange (BSE) and National Stock Exchange (NSE) operate on IST.
GMT – Greenwich Mean Time
UTC+00:00Greenwich Mean Time (GMT) is the mean solar time at the Royal Observatory in Greenwich, London. It is the same as UTC+00:00.
- •GMT is based on the Prime Meridian (0° longitude) passing through Greenwich, London.
- •The Royal Observatory in Greenwich has been the reference point for GMT since 1884.
- •GMT and UTC are often used interchangeably, but UTC is based on atomic clocks.
- •Iceland uses GMT year-round and never observes daylight saving time.
- •The UK switches from GMT to BST (British Summer Time) in late March each year.
About London
WikipediaLondon, where Greenwich Mean Time (GMT) originates, is the world's leading financial center alongside New York. The city bridges European and American business hours.
Big Ben is actually the name of the bell inside the Elizabeth Tower, not the tower itself.
IST vs London: Offsets, DST and Best Call Times
IST runs on India Standard Time (IST) at UTC+05:30. London runs on British Summer Time (BST) at UTC+01:00, also currently on daylight saving time. That puts IST 4 hours 30 minutes behind London — a difference of -4h 30m at the current offsets.
In practice, when it is 9:00 AM in IST it is 4:30 AM in London. Midnight in IST is 7:30 PM in London.London observes daylight saving time while IST does not, so the gap narrows or widens by an hour part of the year.
IST to London time conversion table
| IST (IST) | London (BST) | Day |
|---|---|---|
| 12:00 AM | 7:30 PM | previous day |
| 6:00 AM | 1:30 AM | same day |
| 7:00 AM | 2:30 AM | same day |
| 8:00 AM | 3:30 AM | same day |
| 9:00 AM | 4:30 AM | same day |
| 12:00 PM | 7:30 AM | same day |
| 3:00 PM | 10:30 AM | same day |
| 5:00 PM | 12:30 PM | same day |
| 6:00 PM | 1:30 PM | same day |
| 9:00 PM | 4:30 PM | same day |
Why people convert IST to London time
- Scheduling a call from IST to London: a 10:00 AM start in IST lands at 5:30 AM in London, so you can confirm the slot without doing the arithmetic yourself.
- Finding shared working hours: both IST and London are inside the 9-to-5 working day between 1:30 PM and 5:00 PM IST time (9:00 AM–12:30 PM BST). That is roughly 3 hours 30 minutes of usable overlap.
- Booking travel or deliveries: tracking London local time against IST keeps pickup windows and arrival estimates honest across the -4h 30m offset.
- Always state the zone abbreviation, not just the hour. "3:00 PM IST" is unambiguous; "3 PM" across a -4h 30m gap is not.
- Block 1:30 PM–5:00 PM IST as the recurring meeting window if you work primarily from IST and need London colleagues present.
- London: Clocks fall back on Sun, Oct 25, 2026. Any meeting series spanning that date will shift by an hour in local time.
About IST (India Standard Time)
India Standard Time (IST) is the time observed throughout India and Sri Lanka. It is based on the 82.5°E meridian, passing through Mirzapur in Uttar Pradesh. India uses a single time zone despite spanning roughly 30° of longitude, which has been debated. IST does not observe daylight saving time. India is the world's most populous country, making IST one of the most-used time zones globally. The IT outsourcing industry and call centers operate primarily on IST, making the EST-to-IST conversion one of the most searched timezone conversions.
About GMT (Greenwich Mean Time)
Greenwich Mean Time (GMT) is the clock time at the Royal Observatory in Greenwich, London, which sits on the Prime Meridian (0° longitude). GMT serves as the reference point from which all other time zones are calculated. The United Kingdom uses GMT during winter months and switches to British Summer Time (BST, UTC+01:00) from late March to late October. Several West African nations use GMT year-round. GMT is often used interchangeably with UTC (Coordinated Universal Time), although technically they are different – UTC is based on atomic clocks while GMT is based on Earth's rotation.
Best time to call between IST and London
Both IST and London sit inside the 9 AM – 5 PM working day between 1:30 PM–5:00 PM IST, which is 9:00 AM–12:30 PM BST. That gives roughly 3 hours and 30 minutes of shared time — the safest window for a live call or meeting.
Business hours overlap
IST and London overlap for about 3 hours during the working day — enough for meetings if you avoid the edges of the window.
IST is 4 hours 30 minutes behind London (IST UTC+05:30 → BST UTC+01:00). The shared working window is 1:30 PM–5:00 PM IST. Remember to re-check around daylight-saving transitions.
🕐 Daylight Saving Time Info
IST
Does not observe DST
London
☀ Currently in DST
Standard: UTC+00:00 · DST: UTC+01:00
Clocks fall back on Sun, Oct 25, 2026
Learn More About Time
Dive deeper into the fascinating world of timekeeping, time zones, and how they shape our global society:
Frequently Asked Questions
What is the time difference between IST and London?
IST (IST, UTC+05:30) is 4 hours 30 minutes behind London (BST, UTC+01:00). The gap is currently -4h 30m.
How do I convert IST time to London time?
Add -4h 30m to IST local time. For example, 9:00 AM in IST is 4:30 AM in London.
What time is it in London right now?
London uses BST at UTC+01:00. Use the live converter at the top of this page — it updates in real time and already accounts for the -4h 30m offset from IST.
What is the best time to call London from IST?
Call between 1:30 PM and 5:00 PM IST — that maps to 9:00 AM–12:30 PM BST and keeps both parties inside the working day.
Which is behind, IST or London?
IST is 4 hours 30 minutes behind London. When it is 12:00 PM in IST it is 7:30 AM in London.
Do IST and London use different time zones?
IST uses IST at UTC+05:30, while London (UK) uses BST at UTC+01:00. The IANA identifiers are Asia/Kolkata and Europe/London.
Does daylight saving time affect the IST–London difference?
Yes at the moment: London is on daylight saving time and IST is not, so the -4h 30m gap shifts by an hour when exactly one of them changes clocks.
Which other cities share IST's time zone?
IST also covers Mumbai, Delhi, Bangalore, Kolkata, Chennai, Hyderabad, Pune, Ahmedabad and 4 more.
Which countries use IST, IST's zone?
IST is used in India, Sri Lanka.
Is there a day difference between IST and London?
Not normally. The -4h 30m gap only pushes the date over the previous day.
What is the time difference between IST and London?
London is -4h 30m from IST.
What timezone is IST in?
IST operates on its local timezone.
What timezone is London in?
London, where Greenwich Mean Time (GMT) originates, is the world's leading financial center alongside New York. The city bridges European and American business hours.
What are the business hours in London?
Standard business hours in London are 9:00 AM - 5:00 PM GMT.
Which countries use IST (India Standard Time)?
IST is used in India, Sri Lanka.
Does IST observe daylight saving time?
No, IST does not observe daylight saving time and remains at UTC+05:30 year-round.
What are some interesting facts about IST?
India is 10 hours 30 minutes ahead of EST and 5 hours 30 minutes ahead of GMT. India uses a single time zone despite spanning 30° of longitude.
Which cities are in the GMT timezone?
Major cities in the GMT timezone include London, Dublin, Lisbon, Accra, Reykjavik, Edinburgh, Casablanca, Dakar.
What is the UTC offset for GMT?
Greenwich Mean Time (GMT) is at UTC+00:00. During daylight saving time, it shifts to BST.
What should I know about the GMT timezone?
GMT is based on the Prime Meridian (0° longitude) passing through Greenwich, London. The Royal Observatory in Greenwich has been the reference point for GMT since 1884.
When is it midnight in IST, what time is it in London?
When it is 12:00 AM (midnight) in IST (IST), it is -4h 30m later in London (GMT).
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