Convert IST to GMT India Standard Time ↔ Greenwich Mean Time Free Online Secure
Type a time in IST and read it in GMT straight away. The offset is −5:30 h, the arithmetic wraps at midnight, and the answer says which day it lands on.
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Through the day — Convert IST to GMT (India Standard Time ↔ Greenwich Mean Time)
| IST | GMT |
|---|---|
| 00:00 | 18:30 |
| 03:00 | 21:30 |
| 06:00 | 00:30 |
| 09:00 | 03:30 |
| 12:00 | 06:30 |
| 15:00 | 09:30 |
| 18:00 | 12:30 |
| 21:00 | 15:30 |
Where these units come from
Until the middle of the nineteenth century every town kept its own noon, set by the sun overhead, and nobody minded that the next town was four minutes behind. Railways ended that: a timetable cannot be written for a hundred local noons. Britain put its railways on Greenwich time in 1847, and in 1884 the International Meridian Conference in Washington chose Greenwich as the prime meridian and sketched the twenty-four-hour scheme we still use. Greenwich Mean Time was the world's reference until 1972, when Coordinated Universal Time replaced it: UTC is kept by atomic clocks and tied back to the turning Earth by leap seconds. The abbreviations on this page name standard time — the winter setting — which is why each one is a fixed number of hours rather than something that drifts through the year.
Where you meet them
A time zone becomes real the moment two people in different places have to agree on one moment: a call between offices, a flight that lands before it took off, a market that opens while you are asleep, a deadline written in somebody else's afternoon. Server logs, train and flight schedules and anything stamped with a time are kept in UTC precisely so that the question can always be settled, no matter whose clock was on the wall.
Questions people ask
What about summer time?
The offsets here are standard-time offsets, the ones a zone keeps in winter. Where summer time is observed, the same places move one hour further on for part of the year and take a different name: Central European Time becomes Central European Summer Time, Eastern Standard Time becomes Eastern Daylight Time. The switching dates are not the same in every country, and the two hemispheres change in opposite months, so for a date inside a summer-time period add an hour to whichever side observes it.
Why isn't every difference a whole number of hours?
Because offsets are decided by governments, not by geometry. India is half an hour off the hour, at UTC+05:30; Nepal is three quarters, at UTC+05:45; the Chatham Islands are at UTC+12:45. Any of these can be changed by law, and several countries have moved their offset within living memory.
Is the answer exact?
Where both units are defined in terms of one another by whole numbers, yes — the page says so above the figure, and the only rounding is in how many digits are shown. Where the ratio has no finite decimal, the page shows twelve significant digits and says the relation is approximate rather than pretending otherwise.
Does anything I type leave my device?
No. The arithmetic runs in your browser; nothing is uploaded and there is no server to upload it to. Load the page once and it keeps working with the network switched off.
Putting an Indian time on a Greenwich clock
An Indian space launch is announced for 14:35. The Union Budget will be read at 11:00. Counting of votes begins at 08:00. Each time is stated in Indian Standard Time, and each reader in Britain, Ireland, Iceland or West Africa who wants to follow the event live must convert IST to GMT. Subtract five hours and thirty minutes: 14:35 IST is 09:05 GMT, 11:00 IST is 05:30 GMT, and 08:00 IST is 02:30 GMT. Any Indian time before 05:30 belongs to the previous date at Greenwich, so 04:00 IST is 22:30 GMT the day before.
Below you will find the rule, two lookup tables, a profile of each zone, an explanation of what happens to the gap in British summer time, and examples drawn from space missions, national budgets, elections, visa offices and festivals. The calculation is done in your browser and nothing you type is uploaded.
The subtraction in detail
Remove five and a half hours
IST is UTC+5:30 and GMT is UTC+0, so Greenwich is 5 hours and 30 minutes behind. Take that amount from the Indian time each time you convert IST to GMT. If the answer would be negative, add 24 hours and use the previous date. 03:10 IST gives −2:20, which is 21:40 GMT the day before.
Eight pairs to remember
00:30 IST is 19:00 GMT the previous day. 06:15 IST is 00:45 GMT. 09:00 IST is 03:30 GMT. 12:00 IST is 06:30 GMT. 15:45 IST is 10:15 GMT. 18:00 IST is 12:30 GMT. 21:30 IST is 16:00 GMT. 23:45 IST is 18:15 GMT. Only the first row falls on the earlier date.
Take six, give back thirty
An easy way to do it in your head is to subtract six hours and then add thirty minutes. For 17:00 IST, 17 minus 6 is 11, plus thirty minutes is 11:30 GMT. The route works for any time you convert IST to GMT, because 5:30 is six hours less half an hour.
India’s single clock
Why the half hour
Indian Standard Time, the zone you need before you convert IST to GMT, is based on the meridian at 82.5 degrees east, close to the middle of the country. Dividing 82.5 by 15 gives exactly 5.5 hours, which is why India’s offset from Greenwich is five and a half hours and not a whole number. The standard was introduced in 1906 and kept after independence.
One zone, a wide country
Though India stretches almost thirty degrees from west to east, it has one zone and no summer time. Sri Lanka uses the same offset. Nepal sits at UTC+5:45, Pakistan at UTC+5 and Bangladesh at UTC+6.
Beware of the abbreviation
IST also stands for Irish Standard Time and Israel Standard Time. The converter on this page always means India.
Greenwich Mean Time as the destination
Where you find it
GMT is the winter clock of Britain and Ireland, the permanent clock of Iceland and several African countries, and the label of the zero-offset reference in network headers and logs.
London in summer
From 29 March to 25 October 2026, London reads BST, UTC+1. A London wall clock is then only 4 hours and 30 minutes behind India. The true zero meridian, which you see in logs, remains 5 hours and 30 minutes behind throughout the year.
A small overlap in the working day
Two and a half shared hours
An Indian office day of 09:00 to 17:00 IST corresponds to 03:30 to 11:30 GMT. A London day of 09:00 to 17:00 GMT corresponds to 14:30 to 22:30 IST. The only shared stretch lies between 09:00 and 11:30 GMT, or 14:30 and 17:00 IST: two and a half hours.
Messages and replies
An e-mail sent from India at 14:30 IST, once you convert IST to GMT, reaches London at 09:00 GMT, the start of the British day, so a reply can arrive before lunch. One sent at 18:30 IST reaches London at 13:00 GMT, and the answer comes back overnight, in the Indian early morning.
By air to Britain
A flight that leaves Delhi at 03:00 IST leaves at 21:30 GMT the previous evening, and after about nine and a half hours lands at 07:00 GMT. The ticket shows 03:00 and 07:00, which looks like a four-hour trip.
When the gap is half an hour smaller than you think
Only London moves
India does not change its clocks. London does, on 29 March and 25 October 2026. In between, the gap is 4:30 rather than 5:30. A change of one hour in the offset arises from a decision taken in Britain, not in India.
Numbers from the calendar
From 25 October 2026 to 28 March 2027, London reads GMT and the gap is 5:30. From 29 March to 24 October 2026, London reads BST and the gap is 4:30. An event at 19:30 IST is at 14:00 GMT in winter and 15:00 BST in summer.
What to do with the answer
The form above subtracts 5:30. If the date falls in British summer time and you want the London wall clock, add one hour to the answer. If you want the zero meridian, leave it as it is.
Launches from Sriharikota
A lunar mission in the afternoon
The Chandrayaan-3 lunar mission lifted off on 14 July 2023 at 14:35 IST, which was 09:05 GMT. The landing took place on 23 August 2023 at about 18:04 IST, or 12:34 GMT. For viewers in Britain, both events fell in daylight, in the morning and the early afternoon.
Night launches
Launch windows given as 06:00 to 06:30 IST are 00:30 to 01:00 GMT. Anyone who intends to watch from London must set an alarm for the middle of the night, and a short convert IST to GMT the day before shows exactly when.
Budget day and election counts
The budget speech
The Union Budget is normally presented on 1 February at 11:00 IST, which is 05:30 GMT. Analysts in London, who start work at 08:00, read the main figures about two and a half hours after the announcement.
Counting day
On the day of results, counting starts at 08:00 IST, which is 02:30 GMT. The first trends appear after about 09:00 IST, or 03:30 GMT. A follower in Britain who wakes at 06:30 GMT sees most of the early tallies already in place.
Indian shares and British investors
The session
The major Indian exchanges trade from 09:15 to 15:30 IST, which is 03:45 to 10:00 GMT. A fund manager in London who looks at the Indian market at 08:00 GMT sees it in its last two hours. By the time London trades at 10:00, the Indian session is over.
Currency quotes
Banks in London that quote rupee rates for corporate customers check the Indian close from the previous day, 15:30 IST or 10:00 GMT, before they open their desks at 08:00 GMT the next morning. A rate that was struck at 14:00 IST was struck at 08:30 GMT.
Cricket for viewers abroad
The Indian Premier League
Matches in the league start at 15:30 IST or 19:30 IST, which are 10:00 or 14:00 GMT. A British fan watches the afternoon game at lunchtime and the evening game in the mid-afternoon, which makes the whole season easy to follow from a desk.
Day-night internationals
One-day internationals starting at 13:30 IST begin at 08:00 GMT and finish around 22:00 IST, or 16:30 GMT. A fan who prefers to watch the full match finds that British afternoons are filled with Indian evenings. A “convert IST to GMT” calculation for each fixture provides the right alarm.
UK visa and passport appointments
Booking from India
Application centres in India open at about 09:00 IST, or 03:30 GMT. An appointment at 10:30 IST is at 05:00 GMT, long before a British caseworker begins the day. Applicants who ask a relative in Britain to call the helpline should convert IST to GMT first, to choose a time when the British side is awake: after 14:30 IST, or 09:00 GMT.
Deadlines
A form submitted at 23:50 IST on 31 March is submitted at 18:20 GMT on 31 March. A rule that says “midnight UK time” gives the Indian applicant 5:30 more in winter and 4:30 more in summer, so check which clock the office is using.
Weddings and family events streamed abroad
The auspicious time
A Hindu wedding ceremony is often set for a moment chosen by an astrologer, such as 20:41 IST, which is 15:11 GMT. Relatives in Britain who watch online must join in the afternoon. A morning rite at 09:15 IST is at 03:45 GMT, and most guests watch a recording.
Planning the guest list
Families often send invitations that show only the Indian time, which leaves every guest abroad to convert IST to GMT alone. A short note with the GMT equivalent helps relatives in Britain, and a table at the bottom of the card lets everyone in Europe and the Middle East find their own hour.
Streaming premieres from Mumbai
Midnight in India
Films and series on streaming services often become available at midnight Indian time. That is 18:30 GMT the previous day, early evening in Britain. Viewers in London can watch a premiere before their own midnight arrives.
Cinema release days
Early shows in Indian cinemas begin at about 09:00 IST, or 03:30 GMT, and evening shows at 21:00 IST, or 15:30 GMT. Reviews published by Indian newspapers after the evening show reach British readers in the afternoon.
Every hour in one table
IST to GMT
00:00 IST is 18:30 GMT (previous day). 01:00 IST is 19:30 GMT (previous day). 02:00 IST is 20:30 GMT (previous day). 03:00 IST is 21:30 GMT (previous day). 04:00 IST is 22:30 GMT (previous day). 05:00 IST is 23:30 GMT (previous day). 06:00 IST is 00:30 GMT. 07:00 IST is 01:30 GMT. 08:00 IST is 02:30 GMT. 09:00 IST is 03:30 GMT. 10:00 IST is 04:30 GMT. 11:00 IST is 05:30 GMT. 12:00 IST is 06:30 GMT. 13:00 IST is 07:30 GMT. 14:00 IST is 08:30 GMT. 15:00 IST is 09:30 GMT. 16:00 IST is 10:30 GMT. 17:00 IST is 11:30 GMT. 18:00 IST is 12:30 GMT. 19:00 IST is 13:30 GMT. 20:00 IST is 14:30 GMT. 21:00 IST is 15:30 GMT. 22:00 IST is 16:30 GMT. 23:00 IST is 17:30 GMT.
How to read it
Each entry pairs an Indian hour with the matching Greenwich hour and says when the date moves. Note how every :00 becomes :30, as always when you convert IST to GMT.
Ten readings with minutes
Examples
01:05 IST is 19:35 GMT (previous day). 03:20 IST is 21:50 GMT (previous day). 05:50 IST is 00:20 GMT. 07:35 IST is 02:05 GMT. 10:10 IST is 04:40 GMT. 13:25 IST is 07:55 GMT. 16:40 IST is 11:10 GMT. 19:55 IST is 14:25 GMT. 22:15 IST is 16:45 GMT. 23:05 IST is 17:35 GMT.
The minutes change
Because the offset includes half an hour, the minutes change by thirty. If the minutes in your answer are the same as in the question, the conversion was not for this pair.
What part of the day is it in London?
Greenwich hours for the Indian day
06:00 IST is 00:30 GMT (night). 08:00 IST is 02:30 GMT (night). 10:00 IST is 04:30 GMT (night). 12:00 IST is 06:30 GMT (early morning). 14:00 IST is 08:30 GMT (morning). 16:00 IST is 10:30 GMT (morning). 18:00 IST is 12:30 GMT (around midday). 20:00 IST is 14:30 GMT (afternoon). 22:00 IST is 16:30 GMT (afternoon).
Using the list
The words in brackets describe the part of the day at Greenwich. They tell you at a glance whether a call is convenient.
Neighbouring zones in Asia
From Indian time
Subtract 5:30 for GMT, 1:30 for Dubai and 0:30 for Pakistan. Add 0:15 for Nepal, 0:30 for Bangladesh, 2:30 for China and Singapore and 3:30 for Japan.
One moment on five clocks
When it is 12:00 in Mumbai, it is 06:30 in London, 10:30 in Dubai, 12:30 in Dhaka and 15:30 in Tokyo. Listing the five in a message spares each reader a separate convert IST to GMT.
Dated examples
Mid-winter
At 15:30 in India on the 13th of January, Greenwich shows 10:00. Neither country is on summer time, so the standard gap of 5:30 applies.
The last week of winter in Britain
At 15:30 IST on 24 March, Greenwich still shows 10:00, since London does not move its clocks until 29 March.
High summer
At 15:30 IST on 14 July, a London wall clock shows 11:00 BST, while a zero-meridian log shows 10:00 UTC. The gap to London is 4:30.
Early November
At 15:30 IST on 10 November, Greenwich shows 10:00 again, because London went back on 25 October.
Checklist: how to convert IST to GMT
Before
Read the label
IST can mean India, Ireland or Israel. Here it means India.
Check the season
Between 29 March and 25 October 2026 the London wall clock is on BST, and the gap is 4:30.
After
Subtract 5:30
If the answer is negative, add 24 and use the previous date.
Check the early hours
Any Indian time between 00:00 and 05:29 belongs to the previous date in London.
Doctors and hospitals abroad
Remote consultations with Chennai and Delhi
Large Indian hospitals offer video consultations for patients in Britain. A slot at 16:00 IST is at 10:30 GMT, and one at 18:30 IST is at 13:00 GMT. A British patient who wants an appointment after work chooses 21:00 IST, which is 15:30 GMT, when many clinics have closed. The hospital will often list the slot in Indian time only.
Reports and prescriptions
A report signed at 07:15 IST is dated 01:45 GMT. A prescription issued at 23:50 IST on a Friday is issued at 18:20 GMT on the same Friday. When a British pharmacy asks for the date of issue, make sure the date matches the clock you used.
Tea auctions in Kolkata and Guwahati
An early start
Tea auctions in eastern India commence in the morning, around 10:00 IST, which is 04:30 GMT. Buyers who bid from London must be online before dawn. Results appear in the afternoon, at about 15:00 IST, or 09:30 GMT, just as the London market opens.
Shipping documents
Export paperwork carries local times. A shipment loaded at 17:45 IST on 8 June is loaded at 12:15 GMT on the same date. A buyer who converts all entries to GMT can compare them with the schedule of the British port.
Mistakes when you convert IST to GMT
Dropping the thirty minutes
Subtracting only five hours leaves an answer thirty minutes too late.
Using six hours
Six hours is the Bangladesh figure. India is 5:30 and Nepal 5:45.
Forgetting British summer time
Against the London wall clock the gap is 4:30 in summer. India did not change; London did.
Keeping the date
03:00 IST is 21:30 GMT the previous evening. Copying the date produces a 24-hour error.
Frequently asked questions
By how much do IST and GMT differ?
By five and a half hours, with India in front.
Which formula do I use to convert IST to GMT?
Subtract 5:30 from the Indian time, and add 24 hours if the answer is below zero.
How much is 11:00 IST in GMT?
05:30 GMT.
Is the gap constant through the year?
Against the zero meridian, yes. Against the London wall clock, it shrinks to 4:30 in British summer time.
Does the page store what I type?
No. Everything is processed in your browser.
More time zone converters
Related pages: Convert IST to CST, Convert IST to WET, Convert UTC to GMT, Convert WET to GMT, Convert GMT to EET, Convert EST to IST, Convert IST to UTC, Convert EST to WET, Convert GMT to CET. The opposite direction is Convert GMT to IST.
To sum up, a request to convert IST to GMT means taking away five and a half hours, minding the minutes and the early hours of the morning, and keeping British summer time in mind. All of it happens on your own device, with no account.