Convert GMT to IST Greenwich Mean Time ↔ India Standard Time Free Online Secure
Type a time in GMT and read it in IST 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 GMT to IST (Greenwich Mean Time ↔ India Standard Time)
| GMT | IST |
|---|---|
| 00:00 | 05:30 |
| 03:00 | 08:30 |
| 06:00 | 11:30 |
| 09:00 | 14:30 |
| 12:00 | 17:30 |
| 15:00 | 20:30 |
| 18:00 | 23:30 |
| 21:00 | 02:30 |
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.
A zone with a half hour in it
India is the only major country whose clocks stand on a half hour. Indian Standard Time is five hours and thirty minutes ahead of Greenwich Mean Time, so a request to convert GMT to IST cannot be answered by adding a whole number of hours. 09:00 GMT is 14:30 IST, 12:00 GMT is 17:30 IST, and 18:30 GMT is midnight in Delhi on the following date. The minutes change in every conversion, and the date changes for every GMT reading from 18:30 onward.
This page shows how to do the arithmetic without mistakes, gives lookup tables, describes both zones, explains why the gap shrinks to four and a half hours during British summer time, and runs through practical cases ranging from support centres to Test cricket and from flights to festivals. All of the calculation takes place in your browser, and nothing you type is uploaded.
How to convert GMT to IST
Add five hours and thirty minutes
IST is UTC+5:30 and GMT is UTC+0. Add 5 hours and 30 minutes to the GMT time whenever you convert GMT to IST. If the total reaches 24:00, subtract 24 hours and advance the date. 20:15 GMT plus 5:30 is 25:45, which is 01:45 IST on the following day.
Eight readings to check yourself
00:30 GMT is 06:00 IST. 06:15 GMT is 11:45 IST. 09:00 GMT is 14:30 IST. 12:00 GMT is 17:30 IST. 15:45 GMT is 21:15 IST. 18:00 GMT is 23:30 IST. 21:30 GMT is 03:00 IST the next day. 23:45 GMT is 05:15 IST the next day. The last two cross the date boundary.
The mental shortcut
Add six hours and take off thirty minutes. For 16:20 GMT, six hours gives 22:20, and subtracting half an hour leaves 21:50 IST. The method works every time you convert GMT to IST, because 5:30 is exactly six hours minus thirty minutes.
Indian Standard Time
One zone for a whole subcontinent
India spans nearly thirty degrees of longitude, which would suit two or three time zones, but the country keeps one: UTC+5:30. It was introduced in 1906 and kept after independence. As a result the Sun rises almost two hours earlier in Assam than in Gujarat, though the clocks show the same hour. The tea gardens of Assam once ran their own “tea time”, an hour ahead of the national clock.
No summer time
India does not change its clocks. IST remains at UTC+5:30 all year, so the gap with London varies only because London moves. Sri Lanka shares the same offset, Nepal uses UTC+5:45, Pakistan UTC+5 and Bangladesh UTC+6.
Other ISTs
The abbreviation IST can also mean Irish Standard Time or Israel Standard Time. This converter always means India.
Greenwich Mean Time from the Indian side
The British clock
GMT is the winter time of Britain and Ireland. From 29 March to 25 October 2026 the British wall clock reads BST, UTC+1, an hour ahead. GMT is also the name used in network headers and logs for the zero-offset reference, which coincides with UTC.
A shared history
Before 1906 India had several local times: Bombay time, Calcutta time and Madras time, each tied to a local meridian. The railways and telegraph pushed the country towards a common standard. The one chosen, five and a half hours ahead of Greenwich, was close to the middle of the country’s width.
Office hours that barely touch
The overlap
An Indian office open from 09:00 to 17:00 IST is open from 03:30 to 11:30 on the Greenwich clock. A London office open from 09:00 to 17:00 GMT is open from 14:30 to 22:30 IST. The two days overlap from 09:00 to 11:30 GMT, which is 14:30 to 17:00 IST: just two and a half hours.
Who stays late, who starts early
Teams in Bangalore, Hyderabad and Pune who serve British clients often work a shifted day, from 12:00 to 20:00 IST, which is 06:30 to 14:30 GMT. London colleagues who start at 09:00 therefore meet the Indian team at the end of its day.
By air from Heathrow
A flight leaving London at 14:00 GMT and lasting about eight and a half hours lands at 22:30 GMT, which is 04:00 in Delhi on the next morning. The boarding pass shows 14:00 and 04:00, so the journey seems to last fourteen hours.
Four and a half hours in summer
One side moves
London changes its clocks, India does not. In winter the gap is 5:30. From 29 March to 25 October 2026, when London is on BST, UTC+1, the gap falls to 4:30. A call at 15:00 London time is at 20:30 IST in January and at 19:30 IST in July.
The practical effect
Families who often have to convert GMT to IST for relatives in Britain and India notice that the best hour for a call appears to move by an hour twice a year. They sometimes blame the Indian side, though India has changed nothing at all.
What the calculator uses
The form above applies the winter figure of 5:30. For a date in British summer time, subtract an hour from the result. For example, 12:00 GMT in January is 17:30 IST, but 12:00 BST in July is 16:30 IST.
England touring India
Match hours
When England tour India, Test matches begin at 09:30 IST, which is 04:00 GMT. Lunch is at 11:30 IST, or 06:00 GMT, and play ends around 16:30 IST, or 11:00 GMT. A supporter in Britain who wakes at 06:00 GMT therefore catches the second session and the afternoon, but not the first ball.
Day-night matches
Under floodlights the start moves later. A day-night Test starting at 13:30 IST begins at 08:00 GMT, a civilised hour for a British viewer. When you convert GMT to IST for each session, you can plan breakfast around the first ball.
Support centres for British companies
Shifts that follow the sun
Many UK banks, retailers and telecoms firms use contact centres in India. A shift from 13:00 to 21:00 IST is a shift from 07:30 to 15:30 GMT. Customers who ring at 08:00 find the line open, while those who ring at 17:00 are routed to a later team.
How agents handle the offset
Agents note the customer’s time and their own. A callback promised for 15:00 London time is a callback at 20:30 IST in winter. In summer the same promise is a callback at 19:30 IST, so a script that quotes a fixed Indian hour needs updating twice a year.
Flights and the arrival hour
Outbound from Heathrow
Overnight flights to India usually leave Heathrow in the afternoon or evening and arrive in the early morning. A departure at 21:00 GMT, lasting about nine hours, lands at 06:00 GMT, which is 11:30 IST. The traveller loses a night and arrives with the day well advanced.
The way back
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 makes the trip look like four hours, instead of nine and a half.
Calling relatives in Gujarat or Punjab
Best hours for a family call
Large Indian communities in Leicester, Birmingham, Southall and London keep in touch with families in Gujarat and Punjab. A call at 16:00 GMT is at 21:30 IST in winter, a comfortable late evening. In summer, the same 16:00 BST call is at 20:30 IST.
Mornings
A call at 07:00 GMT arrives at 12:30 IST, over lunch. Early calls are best made at weekends, when the British side is not hurrying to work. A short convert GMT to IST before dialling prevents calls that wake grandparents.
Holi and the spring calendar
When the festival of colours falls
In 2026 Holi is celebrated on 4 March. The main street celebrations begin in the morning, from about 09:00 IST, which is 03:30 GMT. British communities organise gatherings on the weekend nearest the date, usually in the afternoon, so that families can attend.
Broadcasts
Temples that stream their ceremonies start at 07:00 IST, which is 01:30 GMT. Viewers abroad who want to join the live broadcast need to do the “convert GMT to IST” calculation the night before.
Planning a tour of Kerala and Goa
Check-in and transfers
Hotels in Kerala list check-in at 14:00 IST, which is 08:30 GMT. An overnight flight that lands in Kochi at 11:30 IST arrives, in British time, at 06:00 GMT. A traveller who wants to rest at the hotel must ask for early check-in.
Backwater cruises
Houseboat cruises start at about 12:00 IST, or 06:30 GMT, and end the next morning at 09:00 IST, or 03:30 GMT. The itineraries are printed in local time, and the offset of five and a half hours is easy to miscalculate on holiday.
Every hour in one table
GMT to IST
00:00 GMT corresponds to 05:30 IST. 01:00 GMT corresponds to 06:30 IST. 02:00 GMT corresponds to 07:30 IST. 03:00 GMT corresponds to 08:30 IST. 04:00 GMT corresponds to 09:30 IST. 05:00 GMT corresponds to 10:30 IST. 06:00 GMT corresponds to 11:30 IST. 07:00 GMT corresponds to 12:30 IST. 08:00 GMT corresponds to 13:30 IST. 09:00 GMT corresponds to 14:30 IST. 10:00 GMT corresponds to 15:30 IST. 11:00 GMT corresponds to 16:30 IST. 12:00 GMT corresponds to 17:30 IST. 13:00 GMT corresponds to 18:30 IST. 14:00 GMT corresponds to 19:30 IST. 15:00 GMT corresponds to 20:30 IST. 16:00 GMT corresponds to 21:30 IST. 17:00 GMT corresponds to 22:30 IST. 18:00 GMT corresponds to 23:30 IST. 19:00 GMT corresponds to 00:30 IST (next day). 20:00 GMT corresponds to 01:30 IST (next day). 21:00 GMT corresponds to 02:30 IST (next day). 22:00 GMT corresponds to 03:30 IST (next day). 23:00 GMT corresponds to 04:30 IST (next day).
How to read it
Each entry pairs a Greenwich hour with the matching Indian hour and says when the date moves. Notice that every minute reading becomes :30, which is characteristic when you convert GMT to IST.
Ten readings with minutes
Examples
01:05 GMT corresponds to 06:35 IST. 03:20 GMT corresponds to 08:50 IST. 05:50 GMT corresponds to 11:20 IST. 07:35 GMT corresponds to 13:05 IST. 10:10 GMT corresponds to 15:40 IST. 13:25 GMT corresponds to 18:55 IST. 16:40 GMT corresponds to 22:10 IST. 19:55 GMT corresponds to 01:25 IST (next day). 22:15 GMT corresponds to 03:45 IST (next day). 23:05 GMT corresponds to 04:35 IST (next day).
Minutes shift by thirty
Unlike most other conversions, the minutes change here: :00 becomes :30, :15 becomes :45, :30 becomes :00 and :45 becomes :15, with the hour carried over. If the minutes stay the same, you used the wrong zone.
What part of the day is it?
The Indian rhythm
06:00 GMT corresponds to 11:30 IST (morning). 08:00 GMT corresponds to 13:30 IST (around midday). 10:00 GMT corresponds to 15:30 IST (afternoon). 12:00 GMT corresponds to 17:30 IST (afternoon). 14:00 GMT corresponds to 19:30 IST (evening). 16:00 GMT corresponds to 21:30 IST (evening). 18:00 GMT corresponds to 23:30 IST (night). 20:00 GMT corresponds to 01:30 IST (night). 22:00 GMT corresponds to 03:30 IST (night).
Using the list
The words in brackets describe the part of the day in India. They help you avoid calling in the middle of the night.
Zones across South and Central Asia
The ladder from Greenwich
Add three hours for Moscow, four for Dubai, five for Pakistan, five and a half for India and Sri Lanka, five and three quarters for Nepal, six for Bangladesh, eight for China and nine for Japan.
One moment on five clocks
When London reads 12:00, Dubai reads 16:00, Mumbai 17:30, Dhaka 18:00 and Tokyo 21:00. A note of this kind spares every reader a separate convert GMT to IST.
Dated examples
January
On Monday 12 January, 10:00 GMT is 15:30 IST. London is on winter time, so the gap is 5:30.
Late March
On Monday 23 March, 10:00 GMT is 15:30 IST. London does not change clocks until 29 March.
July
On Monday 13 July, 10:00 BST is 14:30 IST. The gap is 4:30.
November
On Monday 9 November, 10:00 GMT is 15:30 IST. London has been back on winter time since 25 October.
Checklist: how to convert GMT to IST
Before
Check the label
IST may mean India, Ireland or Israel. Here it is India.
Check the date
From 29 March to 25 October 2026, London is on BST and the gap is 4:30.
After
Add 5:30
If the total reaches 24:00, subtract 24 and advance the date.
Check the date line
GMT hours from 18:30 onward move to the next date.
Bangalore’s engineers and London’s fintech
A partnership across two clocks
London’s financial technology firms and Bangalore’s engineering teams often work as a single unit. A morning sync at 08:30 GMT is a mid-afternoon 14:00 IST for the Indian team, and an end-of-day review at 15:00 IST is at 09:30 GMT, early enough for the London team to read the notes with a coffee. A schedule built around those two moments gives each side about two and a half hours of live contact.
On-call duty
Rotations that hand over responsibility for production systems must name the clock. A handover at 21:00 IST is at 15:30 GMT. When you convert GMT to IST for the rota, state the hours in GMT and give the Indian equivalent in brackets so that engineers on both sides read the same entry.
Night trains across the plains
Timetables in twenty-four hours
Indian Railways publishes timetables on the twenty-four-hour clock, which makes conversion simpler. A sleeper that leaves Delhi at 22:30 IST leaves at 17:00 GMT and may arrive in Kolkata the next afternoon, at 14:00 IST, which is 08:30 GMT. The journey time is the difference between the two local times and has nothing to do with the offset, since both stations share one clock.
Booking from abroad
Online booking engines show departure times in Indian time. A traveller in Britain who books at 23:00 GMT is in fact booking at 04:30 IST on the next date, and the site will often list the departure on that date as well.
The monsoon calendar and travel planning
June to September
The south-west monsoon reaches Kerala in early June and covers most of the country by July. Weather bulletins are issued at fixed hours in IST: an advisory at 08:30 IST appears at 03:00 GMT, and the afternoon bulletin at 17:30 IST at 12:00 GMT. Travellers who check from Britain see the morning update before they go to bed.
Flight disruption
Heavy rain can delay flights in Mumbai. An airline text saying “departure now 18:40” refers to Indian time, which is 13:10 GMT. It helps to remember the offset when you are waiting for a relative at Heathrow.
Mistakes when you convert GMT to IST
Forgetting the half hour
Adding five hours instead of five and a half leaves the answer thirty minutes out.
Using six hours
Six hours is the figure for Bangladesh. India uses 5:30 and Nepal 5:45.
Ignoring British summer time
In summer the gap falls to 4:30. India did not move; London did.
Losing the next date
A deadline at 20:00 GMT is 01:30 IST on the next day. Keeping the date creates a 24-hour error.
Frequently asked questions
How far apart are GMT and IST?
Five hours and thirty minutes, with IST ahead.
How do I convert GMT to IST?
Add 5 hours and 30 minutes. If the total reaches 24:00, subtract 24 and move to the next date.
What is 12:00 GMT in IST?
17:30 IST.
Why does the gap change in summer?
Because London moves to BST while India keeps its clocks unchanged. The gap becomes 4:30.
Is my input uploaded?
No. It stays in your browser.
More time zone converters
Related pages: Convert GMT to EST, Convert GMT to CET, Convert EST to IST, Convert CST to IST, Convert IST to EST, Convert CET to GMT, Convert GMT to EET, Convert EET to CST, Convert EET to CET. For the reverse direction, open Convert IST to GMT.
In brief, to convert GMT to IST you add five and a half hours, watch the minutes and the next date, and remember that British summer time takes an hour off the gap. The work is done locally, with no sign-up and no upload. Anyone who has to convert GMT to IST again tomorrow can simply bookmark this page.