IST to GMT Time Zone Converter
India Standard Time to GMT is the conversion for lining up India's clock with London's. The gap is 5 hours 30 minutes in winter but only 4 hours 30 minutes in summer, because London shifts to British Summer Time from spring to fall while India never changes. The converter tracks which side of that switch your date falls on.
Enter a date and time to convert.
Daylight saving is applied automatically for the date you pick. Labels like PST/EST name the zone (Pacific/Eastern); the real abbreviation shifts to PDT/EDT during daylight saving, and gmt here means London (GMT in winter, BST in summer) while utc stays fixed.
The time difference
London is 5 hours 30 minutes behind India in winter and 4 hours 30 minutes behind in summer. India (Kolkata, Mumbai, Delhi, Bangalore) holds steady at UTC+5:30 all year, but London springs forward for British Summer Time on Mar 29, 2026 and falls back on Oct 25, 2026. Because only London moves, the gap shrinks by an hour across the warmer months.
A worked example
Take 9:00 AM in India. On Jan 15, 2026, when London is on GMT, that is 3:30 AM in London. On Jul 15, 2026, with London on BST, the same 9:00 AM IST lands at 4:30 AM — an hour later on the London clock, because London has shifted while India has not.
Daylight saving & the abbreviation caveat
The name is the catch here. "GMT" is London's winter time; from spring to fall the city runs on BST (British Summer Time), one hour ahead, and locals just say "London time" either way. India never observes daylight saving — it sits at UTC+5:30 all year. So it's always London doing the shifting, never India. The converter picks the right London offset for the exact date you choose, so a summer result that looks an hour off is simply BST at work.
When you'll use it
Scheduling a call between an India team and a London office, catching a UK broadcast or match kickoff, timing a market open on the London exchange, or coordinating remote work hours across the two cities.
Frequently asked questions
How many hours is London behind IST?
5 hours 30 minutes in winter, when London is on GMT. From late March to late October London moves to British Summer Time, which narrows the gap to 4 hours 30 minutes.
Why does the IST to GMT gap change during the year?
India stays fixed at UTC+5:30 all year, but London springs forward an hour for summer. When only one side moves, the difference between them changes by that hour.
Is GMT the same as London time?
In winter, yes. In summer London runs on BST (British Summer Time), one hour ahead of GMT, even though people still loosely call it 'London time.'