Compare MST vs KST
See the 16-hour time difference between MST and KST, understand daylight saving impacts, and find practical meeting hours.
How to Find the Time Difference Between MST and KST
Open the MST to KST converter: Go to https://www.xconvert.com/time-converter/mst-vs-kst to load the comparison grid with Mountain Standard Time (MST) and Korea Standard Time (KST) already shown. This page is useful when you are scheduling a call between teams in places such as Phoenix and Seoul, planning customer support coverage across North America and South Korea, or checking whether a late-afternoon handoff in the U.S. will land during business hours in Korea.
Add other relevant cities with + Add City: Click “+ Add City” and search for cities such as Denver, Los Angeles, or Tokyo to compare nearby business hubs and connected markets. This is especially helpful for companies working across semiconductors, electronics, gaming, manufacturing, and logistics, where U.S. Mountain Time teams may coordinate with suppliers or offices in South Korea and neighboring East Asian time zones.
Drag across the grid to select a meeting window: Click “Select” if needed, then drag across the MST row to highlight a range such as 9:00 AM to 11:00 AM MST; the purple selection will show the matching time in KST as 1:00 AM to 3:00 AM the next day because KST is 16 hours ahead of MST. You can drag the center of the purple block to test alternatives, or resize the left and right handles to find a more practical overlap, such as seeing that 5:00 PM to 7:00 PM MST becomes 9:00 AM to 11:00 AM KST the next day, which is often better for cross-border business calls.
Export and share the selected time: Once your range is selected, use the export options for ICS download, Google Calendar, Gmail, Copy to clipboard, or Share link. For example, a U.S.-Korea product meeting can be sent as an ICS file so both teams see the event in their own local calendars automatically, while the Share link is useful for quickly confirming a handoff time with remote engineering, procurement, or client-facing teams.
MST vs KST Offset Explained
Mountain Standard Time (MST) is UTC-7, while Korea Standard Time (KST) is UTC+9, so KST is exactly 16 hours ahead of MST. That means when it is 9:00 AM MST, it is 1:00 AM KST the following day. Likewise, when it is 6:00 PM in KST, it is 2:00 AM MST on the same calendar day in North America.
The key complication is that MST is a standard-time label, not always the year-round clock used across the entire U.S. Mountain region. Places such as Arizona largely stay on MST all year and do not observe daylight saving time, while places like Denver, Salt Lake City, and Albuquerque switch to Mountain Daylight Time (MDT, UTC-6) during daylight saving months. By contrast, South Korea uses KST year-round at UTC+9 and does not observe DST, so its offset stays stable throughout the year.
In practical terms, the MST-KST difference is 16 hours when comparing KST to true MST (UTC-7), but it becomes 15 hours when a U.S. Mountain location is on MDT (UTC-6). In the United States, daylight saving time in 2025 begins on March 9, 2025, and ends on November 2, 2025. So if you are comparing Phoenix to Seoul, the difference remains 16 hours all year, but if you are comparing Denver to Seoul, the gap is 16 hours in winter and 15 hours from March 9 to November 2, 2025.
This difference matters for real scheduling decisions. A 4:00 PM call in Phoenix converts to 8:00 AM the next day in Seoul, which can work well for morning meetings in Korea. But a 4:00 PM call in Denver during summer converts to 7:00 AM the next day in Seoul, one hour earlier because Denver is then on MDT rather than MST.
For remote teams, the overlap between standard office hours is narrow. A typical 9:00 AM to 5:00 PM KST workday corresponds to 5:00 PM to 1:00 AM MST on the previous day, so late afternoon in the U.S. Mountain zone is usually the best time to reach Korean colleagues during their morning. This is particularly relevant for industries with active U.S.-Korea coordination, including consumer electronics, automotive supply chains, semiconductor manufacturing, e-commerce operations, and online gaming.
Frequently Asked Questions
What is the exact time difference between MST and KST?
KST is 16 hours ahead of MST because MST is UTC-7 and KST is UTC+9. For example, if it is 8:00 AM MST, it is 12:00 AM KST the next day. This large offset usually means meetings happen either in the late afternoon or evening in MST or in the early morning in KST.
Does the time difference between MST and KST change during daylight saving time?
Yes, it can change depending on which North American location you actually mean. If you are using true MST year-round, such as Phoenix, Arizona, the difference to Seoul stays at 16 hours all year because Arizona does not observe DST. If you mean a city like Denver, the winter difference is 16 hours, but during daylight saving time it becomes 15 hours because Denver shifts to MDT (UTC-6) while South Korea stays on KST (UTC+9).
Why does Phoenix have a different seasonal result than Denver when comparing to Seoul?
Phoenix is in Arizona, and most of Arizona stays on MST (UTC-7) all year without switching clocks in spring or fall. Denver, by contrast, follows the U.S. daylight saving schedule and moves from MST to MDT on March 9, 2025, then back on November 2, 2025. That means Phoenix-to-Seoul remains a constant 16-hour gap, while Denver-to-Seoul changes to 15 hours during the DST season.
What is the best meeting time between MST and KST for business calls?
For most teams, the most workable window is late afternoon or early evening in MST, which becomes the next morning in KST. For example, 5:00 PM MST converts to 9:00 AM KST the next day, and 7:00 PM MST converts to 11:00 AM KST, which is often suitable for project reviews, supplier calls, or customer meetings. This pattern is common for U.S.-Korea coordination in technology, manufacturing, procurement, and international trade.
If it is 9 AM in MST, what time is it in KST?
If it is 9:00 AM MST, it is 1:00 AM KST the next day. This shows why a normal morning meeting in the U.S. Mountain zone is usually impractical for colleagues in South Korea, since it falls in the middle of the night there. Teams often shift meetings to 4:00 PM to 7:00 PM MST so Korean participants can join during their 8:00 AM to 11:00 AM workday.
Is South Korea ever on daylight saving time?
No, South Korea currently uses Korea Standard Time (KST, UTC+9) year-round and does not make seasonal clock changes. That consistency makes Seoul easier to plan around than many North American cities, because the Korean side of the conversion never changes. Any seasonal difference you notice usually comes from the U.S. or Canadian location changing between standard time and daylight time.
How do I schedule a call between the U.S. Mountain time zone and South Korea without making a date mistake?
The biggest risk is forgetting that KST is far ahead and often on the next calendar day. For example, 6:30 PM MST on Monday becomes 10:30 AM KST on Tuesday, so the meeting date changes for the Korean side even though the clock time looks straightforward. Using the xconvert visual grid helps because the date row and aligned timelines make it easy to see whether your selected meeting block lands on the same day or the following day.