IST to BST Time Converter
BST is 4 hours and 30 minutes behind IST. IST is UTC+5:30, and BST is UTC+1:00.
Best Time to Call Between IST and BST
Both zones are inside normal business hours between 2:00 PM and 5:00 PM IST — that's 9:30 AM to 12:30 PM BST. That's a 3-hour window.
both at work IST only BST only neither — hours along the strip are IST.
Common Times Converted
IST on the left, BST on the right.
IST to BST: Full 24-Hour Conversion Table
Shaded rows are working hours; the darker shade marks the hours when both zones are at work.
| IST | BST | Working hours |
|---|---|---|
| 12:00 AM | 7:30 PM prev day | — |
| 1:00 AM | 8:30 PM prev day | — |
| 2:00 AM | 9:30 PM prev day | — |
| 3:00 AM | 10:30 PM prev day | — |
| 4:00 AM | 11:30 PM prev day | — |
| 5:00 AM | 12:30 AM | — |
| 6:00 AM | 1:30 AM | — |
| 7:00 AM | 2:30 AM | — |
| 8:00 AM | 3:30 AM | — |
| 9:00 AM | 4:30 AM | IST only |
| 10:00 AM | 5:30 AM | IST only |
| 11:00 AM | 6:30 AM | IST only |
| 12:00 PM | 7:30 AM | IST only |
| 1:00 PM | 8:30 AM | IST only |
| 2:00 PM | 9:30 AM | Both zones |
| 3:00 PM | 10:30 AM | Both zones |
| 4:00 PM | 11:30 AM | Both zones |
| 5:00 PM | 12:30 PM | BST only |
| 6:00 PM | 1:30 PM | BST only |
| 7:00 PM | 2:30 PM | BST only |
| 8:00 PM | 3:30 PM | BST only |
| 9:00 PM | 4:30 PM | BST only |
| 10:00 PM | 5:30 PM | — |
| 11:00 PM | 6:30 PM | — |
What IST and BST Actually Are
IST — India Standard Time
Mumbai, Delhi, Bengaluru, Chennai, Kolkata, Hyderabad — and Colombo. Standing at UTC+5:30 as written, and the region does not change its clocks, so that offset holds all year. IST also stands for Irish Standard Time (UTC+1) and Israel Standard Time (UTC+2). This page covers the Indian one, which is by far the most searched.
India runs a single time zone across a country wide enough for two, which is why sunrise in the north-east can come nearly two hours before Mumbai's. Proposals for a second zone resurface regularly and have never been adopted.
BST — British Summer Time
London, Manchester, Birmingham, Glasgow, and the rest of the UK from late March to late October. Standing at UTC+1:00 as written, and the region does change its clocks, so its live offset moves by an hour twice a year. The next change is on Sunday, October 25, 2026, to GMT. BST also stands for Bangladesh Standard Time (UTC+6). BDT is the clearer label for that one.
British Summer Time began in 1916 as a wartime fuel-saving measure and has run every year since, making it one of the oldest continuous daylight saving schemes in the world.
What This Means in Practice
Expect times on the half hour
IST sits on a 30-minute offset rather than a whole hour, so a round number on one side is never a round number on the other. A 9:00 meeting becomes 30 minutes past the hour, which is exactly the detail calendar invitations get wrong when someone converts in their head.
This gap is not fixed
BST changes its clocks and IST does not, so the difference between them moves by an hour twice a year. A recurring meeting set now will drift for one side from Sunday, October 25, 2026 unless someone resets it.
Major Cities in Each Zone
Cities on IST
Cities on BST
Frequently Asked Questions
What is the time difference between IST and BST?
BST is 4 hours and 30 minutes behind IST.
What is 9:00 AM IST in BST?
9:00 AM IST is 4:30 AM BST.
What are the best hours to schedule a call between IST and BST?
Between 2:00 PM and 5:00 PM IST, which is 9:30 AM to 12:30 PM BST. Both sides are inside normal business hours through that window.
Does the difference between IST and BST change during the year?
Yes. BST observes daylight saving and IST does not, so the gap shifts by an hour at least twice a year. The next clock change is on Sunday, October 25, 2026.
Does IST always mean India Standard Time?
IST also stands for Irish Standard Time (UTC+1) and Israel Standard Time (UTC+2). This page covers the Indian one, which is by far the most searched.
Does BST always mean British Summer Time?
BST also stands for Bangladesh Standard Time (UTC+6). BDT is the clearer label for that one.