Convert CST to IST Central Standard Time ↔ India Standard Time Free Online Secure
Type a time in CST and read it in IST straight away. The offset is +11:30 h, the arithmetic wraps at midnight, and the answer says which day it lands on.
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Through the day — Convert CST to IST (Central Standard Time ↔ India Standard Time)
| CST | IST |
|---|---|
| 00:00 | 11:30 |
| 03:00 | 14:30 |
| 06:00 | 17:30 |
| 09:00 | 20:30 |
| 12:00 | 23:30 |
| 15:00 | 02:30 |
| 18:00 | 05:30 |
| 21:00 | 08:30 |
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.
Garba in Chicago, cricket in Dallas and the clock in Mumbai
A cricket match is played in a Dallas stadium, with the start at 7:00 p.m. CT. The Garba nights in the suburbs of Chicago begin at 7:30 p.m. CT. A report on grain stocks is published in Chicago at 11:00 a.m. CT. For a reader in Mumbai, Bangalore or Delhi, each of those hours calls for a “convert CST to IST” calculation. On standard time the rule is a single line: add eleven and a half hours. 7:00 p.m. CST becomes 06:30 IST the next morning, 7:30 p.m. CST becomes 07:00 IST, and 11:00 a.m. CST becomes 22:30 IST. India does not move its clocks, so the result changes only when America goes onto summer time: from 8 March to 31 October the difference is ten and a half hours.
The page contains the rule, the tables, a description of the zones and episodes from sport, festivals, the grain trade, space research and remote work. The calculation takes place in your browser, and no figure is sent to a server.
Cricket in Texan stadiums
The evening match
A match that starts at 7:00 p.m. CDT in summer starts at 05:30 IST the next morning. Indian fans get up at dawn to watch it live.
The afternoon match
A match at 1:00 p.m. CDT starts at 23:30 IST. For a family in India it is an evening match, watched after dinner. A “convert CST to IST” calculation with the date in view shows that in summer the figure is ten and a half hours.
Garba nights in the Midwest
The dancing evening
The dances of the Navratri nights, starting in October at 7:30 p.m. CDT, begin at 06:00 IST the next morning. Relatives in India watch live at sunrise.
The end of the evening
Toward the end of the evening, at 11:30 p.m. CDT, it is already 10:00 IST in India. Anyone who does a “convert CST to IST” calculation knows that the American evening ends in the middle of the Indian day.
Chicago grain and the Indian market
The federal report
A report published at 11:00 a.m. CST appears at 22:30 IST. Indian pulse traders read it late in the evening.
The trading session
The grain exchange trades between 8:30 a.m. and 1:20 p.m. CST, which is 20:00 to 00:50 IST. A “convert CST to IST” calculation for each line of the timetable shows that it covers the Indian evening.
Houston and Indian space research
The joint briefing
A joint meeting between the teams in Houston and those in India, at 9:00 a.m. CST, is at 20:30 IST. Indian engineers follow it at the end of their working day.
Press conferences
A conference at 2:00 p.m. CST appears at 01:30 IST the following night. Indian journalists write about it the next day.
The Independence Day parade on Devon Avenue
Parade time
The Indian community’s parade in Chicago, held in August, sets off at 12:00 CDT, which is 22:30 IST. Families in India watch in the evening, after dinner.
The evening concert
The concert at 7:00 p.m. CDT begins at 05:30 IST the next morning. A “convert CST to IST” calculation tells you at once whether it is worth watching live.
Diwali in Houston
The evening of lights
The main show of the festival begins at 6:00 p.m. CST, which is 05:30 IST the next morning, if the festival falls after 1 November. If it falls in October, 6:00 p.m. CDT is 04:30 IST.
The prayer in India
The main prayer in India, at 19:00 IST, is at 7:30 a.m. CST or 8:30 a.m. CDT, depending on the date. Families in Texas watch it live at breakfast.
Remote work between Dallas and Bangalore
The morning meeting
A team with members in Dallas and Bangalore meets at 8:00 a.m. CST, which is 19:30 IST. For the Indians it is the end of the day, for the Texans the beginning.
The handover
Work that ends at 5:00 p.m. CST reaches Bangalore at 04:30 IST and waits for the morning. A “convert CST to IST” calculation at each handover shows why written notes are a must.
How to convert CST to IST, in three steps
Step 1: add eleven and a half hours
CST is UTC−6 and India sits at UTC+5:30. Eleven hours 30 minutes separate the two, with India ahead. Write the American time on a 24-hour clock and add 11:30.
Step 2: correct the date
If the total passes 24:00, subtract 24 and go to the next day. That happens for every Central time from 12:30 onward.
Step 3: check against known values
00:30 CST is 12:00 IST. 04:00 CST is 15:30 IST. 07:15 CST is 18:45 IST. 09:00 CST is 20:30 IST. 12:30 CST is 00:00 IST the next day. 15:45 CST is 03:15 IST the next day. 19:00 CST is 06:30 IST the next day. 23:45 CST is 11:15 IST the next day. The last four roll over to the next day.
Central America’s time
Its places
In winter the clocks in Chicago, Dallas, Houston, New Orleans, Minneapolis, Nashville, Winnipeg and all over Mexico read UTC−6. In spring the American states move to UTC−5, under the name CDT.
Exceptions
Mexico and the province of Saskatchewan do not change their clocks. Against India their gap is eleven and a half hours in winter and in summer alike, since neither they nor India moves its clocks.
India’s clock
One clock for a whole country
From Gujarat to Assam, India has never used any clock but UTC+5:30. The half hour changes the minutes of the result: 9:15 a.m. CST becomes 20:45 IST.
The neighbours
Sri Lanka keeps the same time as India. Nepal sits at UTC+5:45, Pakistan at UTC+5, Bangladesh at UTC+6.
Eleven and a half hours between the dials
Office hours
A Chicago office open from 09:00 to 17:00 works, on Indian time, from 20:30 to 04:30. An Indian office open from 09:00 to 17:00 works from 21:30 to 05:30 on the Central clock of the previous day. The two schedules do not touch at all.
Who calls and when
A call from Texas at 8:00 a.m. CST reaches India at 19:30. One at 3:00 p.m. CST reaches 02:30 IST, in the dead of night. That is why calls are made in the morning.
Half the globe by air
A flight with one stop from Chicago to Delhi that leaves at 21:00 CST and takes nearly twenty hours lands at 17:00 CST, which is 04:30 IST, two calendar days after departure. The ticket shows 21:00 and 04:30, as for a trip of thirty-one and a half hours.
Technical support for Texan companies
The evening shift in India
Centres in India serving Texan companies work evenings and nights. A call received at 9:00 a.m. CST is taken at 20:30 IST, and one at 4:00 p.m. CST at 03:30 IST.
What stays in writing
The shift that ends at 04:30 IST hands over its open cases at 5:00 p.m. CST on the previous day. Written notes keep the thread.
Dated examples
January
On Monday 26 January, 09:00 CST is 20:30 IST. The gap is eleven and a half hours.
Early March
On Monday 2 March, 09:00 CST is still 20:30 IST: America has not yet moved its clocks.
Mid-March
On Monday 16 March, 09:00 CDT is 19:30 IST. America moved to summer time on 8 March and India did not, so the gap has shrunk to ten and a half hours.
August and November
On Monday 3 August, 09:00 CDT is 19:30 IST. On Monday 9 November, 09:00 CST is again 20:30 IST, after America’s return to standard time on 1 November.
More Asian clocks, from central America
How many hours to add
From Central time add eleven and a half hours for India, eleven and three-quarters for Nepal, fourteen for China and Singapore and fifteen for Japan. On American summer time, subtract one hour from each.
One instant on four clocks
When it is 9:00 a.m. in Chicago in winter, it is 20:30 in Delhi, 21:00 in Dhaka, 23:00 in Singapore and 00:00 the next day in Tokyo. Whoever writes all the hours in the invitation spares the guests a “convert CST to IST” calculation.
Video calls between relatives in Texas and India
The best hour for both sides
The best time for a video call is the Texan morning: 7:00 a.m. CST means 18:30 IST, dinner time in India. A call at 3:00 p.m. CST would arrive at 02:30 IST, when the grandparents are asleep.
Birthdays
The morning of a birthday in India, at 07:00 IST, is at 7:30 p.m. CST on the previous evening. A “convert CST to IST” calculation made beforehand shows why greetings from Texas arrive a day early.
Online courses from Texan universities
Course time
A lecture at 10:00 a.m. CST is at 21:30 IST. Students in India follow it in the evening, after their usual hours.
Deadlines
A deadline of 11:59 p.m. CST falls at 11:29 IST the next day. An Indian student who counts the deadline as midnight on their own clock actually has almost twelve hours more.
The Indian film festival in Dallas
Evening screenings
A gala screening at 7:00 p.m. CST starts at 06:30 IST the next morning. Film lovers in India watch the stream at dawn.
Panel talks
A panel with directors at 1:00 p.m. CST is at 00:30 IST. A “convert CST to IST” calculation made beforehand shows that for India it falls just after midnight.
Plains storms, read from India
The time of the bulletin
A warning valid until 9:00 p.m. CST expires at 08:30 IST the next day. Relatives in India who follow events write the local time beside it.
How to read it
Each bulletin carries the local time of central America. A “convert CST to IST” calculation for both times shows when the latest version appeared.
How the clock changes affect this pair
Period by period
CST and IST are not always the same distance apart. In 2026: 1 January to 7 March and 1 November to 31 December: IST is 11 hours 30 minutes ahead of CST; 8 to 28 March, 29 March to 24 October and 25 to 31 October: IST is 10 hours 30 minutes ahead of CST.
How to apply it
Summer labels are CDT and IST. The form above applies the winter gap of 11 hours 30 minutes, so for other periods correct the answer by the difference from the figure listed. Whenever you convert CST to IST, check which period the date falls in first.
Every hour in one table
CST to IST
00:00 CST becomes 11:30 IST. 01:00 CST becomes 12:30 IST. 02:00 CST becomes 13:30 IST. 03:00 CST becomes 14:30 IST. 04:00 CST becomes 15:30 IST. 05:00 CST becomes 16:30 IST. 06:00 CST becomes 17:30 IST. 07:00 CST becomes 18:30 IST. 08:00 CST becomes 19:30 IST. 09:00 CST becomes 20:30 IST. 10:00 CST becomes 21:30 IST. 11:00 CST becomes 22:30 IST. 12:00 CST becomes 23:30 IST. 13:00 CST becomes 00:30 IST (next day). 14:00 CST becomes 01:30 IST (next day). 15:00 CST becomes 02:30 IST (next day). 16:00 CST becomes 03:30 IST (next day). 17:00 CST becomes 04:30 IST (next day). 18:00 CST becomes 05:30 IST (next day). 19:00 CST becomes 06:30 IST (next day). 20:00 CST becomes 07:30 IST (next day). 21:00 CST becomes 08:30 IST (next day). 22:00 CST becomes 09:30 IST (next day). 23:00 CST becomes 10:30 IST (next day).
How to read it
Each row pairs one CST hour with the matching IST hour and says when the date changes. The rows follow the same rule that applies when you convert CST to IST. Unlike most pairs, the minutes change here by thirty: :00 turns into :30, :30 turns into :00 and the hour moves with it. Read these rows as standard-time values and check the period section for dates where the difference changes.
The :30 rows
CST to IST, thirty minutes past
00:30 CST becomes 12:00 IST. 01:30 CST becomes 13:00 IST. 02:30 CST becomes 14:00 IST. 03:30 CST becomes 15:00 IST. 04:30 CST becomes 16:00 IST. 05:30 CST becomes 17:00 IST. 06:30 CST becomes 18:00 IST. 07:30 CST becomes 19:00 IST. 08:30 CST becomes 20:00 IST. 09:30 CST becomes 21:00 IST. 10:30 CST becomes 22:00 IST. 11:30 CST becomes 23:00 IST. 12:30 CST becomes 00:00 IST (next day). 13:30 CST becomes 01:00 IST (next day). 14:30 CST becomes 02:00 IST (next day). 15:30 CST becomes 03:00 IST (next day). 16:30 CST becomes 04:00 IST (next day). 17:30 CST becomes 05:00 IST (next day). 18:30 CST becomes 06:00 IST (next day). 19:30 CST becomes 07:00 IST (next day). 20:30 CST becomes 08:00 IST (next day). 21:30 CST becomes 09:00 IST (next day). 22:30 CST becomes 10:00 IST (next day). 23:30 CST becomes 11:00 IST (next day).
Purpose of the list
These are the readings people forget to check: events at :30. Look up the CST time and read the IST time beside it instead of repeating the calculation. The gap used here is the standard winter one; the period section lists the dates on which it differs.
Odd times, converted
Ten CST times and their IST equivalents
01:05 CST becomes 12:35 IST. 03:20 CST becomes 14:50 IST. 05:50 CST becomes 17:20 IST. 07:35 CST becomes 19:05 IST. 10:10 CST becomes 21:40 IST. 13:25 CST becomes 00:55 IST (next day). 16:40 CST becomes 04:10 IST (next day). 19:55 CST becomes 07:25 IST (next day). 22:15 CST becomes 09:45 IST (next day). 23:05 CST becomes 10:35 IST (next day).
Observation
Real schedules are rarely on the hour, so here are ten with awkward minutes. The half-hour in the offset moves each minute reading by thirty, which is why this pair needs a second look. Read these rows as standard-time values and check the period section for dates where the difference changes.
Times of day in IST
A day in CST, translated into IST
06:00 CST becomes 17:30 IST (afternoon). 08:00 CST becomes 19:30 IST (evening). 10:00 CST becomes 21:30 IST (evening). 12:00 CST becomes 23:30 IST (night). 14:00 CST becomes 01:30 IST (night). 16:00 CST becomes 03:30 IST (night). 18:00 CST becomes 05:30 IST (early morning). 20:00 CST becomes 07:30 IST (early morning). 22:00 CST becomes 09:30 IST (morning).
A practical tip
Read down the list to see how the CST day maps onto the IST day. It is useful before you convert CST to IST for a meeting invitation. Winter-time arithmetic applies to these rows; for the dates in the period section, correct the result accordingly.
Checklist: how to convert CST to IST
First
Read the labels
Beware that CST is also China Standard Time (UTC+8) and Cuba Standard Time (UTC−5); this page uses the North American Central zone. Indian Standard Time is UTC+5:30; the same three letters are used for Israel and for Ireland’s summer clock, which this page does not cover.
Use a 24-hour clock
The 24-hour clock avoids a.m. and p.m. slips, so rewrite 4:30 p.m. as 16:30 before anything else. For example, 09:15 CST becomes 20:45 IST.
Then
The operation
Add 11 hours 30 minutes. If the result passes midnight, correct the date: readings from 12:30 fall on the next date.
A second example
An evening check: 22:40 CST gives 10:10 IST (next day).
Traps to avoid when you convert CST to IST
Subtracting instead of adding
IST is in front of CST: expect a bigger number, not a smaller one.
Losing the date
Anything on the CST clock from 12:30 lands on the next date. Keeping the original date produces a one-day error.
The standard figure in the wrong weeks
The gap between CST and IST is not the same on every date in 2026. Check the period list above before you rely on the standard figure.
Confusing the abbreviation
Three countries share the letters CST; only the North American one, UTC−6, is used on this page. Indian Standard Time is UTC+5:30; the same three letters are used for Israel and for Ireland’s summer clock, which this page does not cover.
Frequently asked questions
How far apart are CST and IST?
11 hours 30 minutes, and IST is ahead of CST. That is the standard figure; on some dates in 2026 it differs, as the period list shows.
What do I do to convert CST to IST?
Add 11 hours 30 minutes to the CST time, then fix the date if the result passes midnight.
What does 21:45 CST become in IST?
09:15 IST on the next day in the standard period.
Do the seasons affect this conversion?
Yes, on some dates; the period list above shows which.
Is the time I enter sent anywhere?
No. Nothing leaves the page.
More time zone converters
See also Convert CST to PST, Convert CST to EET, Convert WET to IST, Convert CET to IST, Convert IST to CET, Convert PST to CST, Convert WET to GMT, Convert IST to UTC, Convert WET to CST. The opposite direction is Convert IST to CST.
The short version: add 11 hours 30 minutes, check the date, and you can convert CST to IST with confidence. No account is needed.