Flight Time
8,375 km
Distance
8,375 km
5,204 mi
Flight Time
10h 11m to 11h 30m
🇺🇸 Seattle → 🇰🇷 Seoul
SEA to ICN — Complete travel planning guide
Time Difference
07:31
Seattle
+16h
difference
23:31
Seoul
Jet Lag Severity
MildModerateSevere
severe
Severity
8
Zones crossed
6d
To adjust
Adjustment Timeline
Day 1
07:00 – 00:00
Day 2
09:00 – 01:00
Day 3
10:00 – 01:00
Day 4
10:00 – 01:00
Day 5
10:00 – 01:00
Day 6
10:00 – 01:00
Evidence-based recommendations
Each recommendation below is graded by how strongly published research supports it, with the source it comes from. Optimal timing depends on your travel direction, the number of time zones crossed and your own circadian phase, so treat the schedule as a starting point.
Seek evening light
StrongBright light in the local evening helps delay your body clock when travelling west.
CDC Yellow Book 2026Limit light in the early morning
StrongEarly light can advance your clock and work against a westward shift during the first days.
NIH — Circadian rhythmsShift bedtime later before departure
ModerateMoving sleep and wake times 30-60 minutes later for a few nights gives your clock a head start on a westward trip.
CDC Yellow Book 2026Live on destination time on arrival
ModerateSleeping, eating and being active on local time gives your body consistent cues about the new day.
CDC Yellow Book 2026Consider timed melatonin
ModerateLow-dose melatonin near the local bedtime can help with sleep timing after crossing several zones; timing matters more than dose.
Cochrane review — Melatonin for jet lagUse caffeine early, not late
Practical adviceCaffeine can help you stay awake during local daytime, but late doses tend to delay sleep onset.
CDC Yellow Book 2026Protect sleep around the flight
Practical adviceArriving without a large sleep debt makes the first days easier, even when few time zones are involved.
CDC Yellow Book 2026
How we grade evidence
- Strong
- Consistently supported by controlled circadian research and current public-health guidance.
- Moderate
- Supported by research, but effect size and best timing vary between individuals and studies.
- Practical advice
- Sensible travel habits with limited direct evidence for shifting the body clock.
This is general travel information, not medical advice. Talk to a clinician before using melatonin or sleep medication, especially if you are pregnant, take other medication or have a sleep disorder.
Flying the other way?Seoul → Seattle
Flying from Seattle to Seoul
The flight from Seattle (SEA) to Seoul (ICN) covers approximately 8,375 kilometers (5,204 miles) based on the great-circle distance between both airports. This is the shortest theoretical path over Earth's surface, though actual flight paths may be slightly longer due to air traffic routing, weather avoidance, and airspace restrictions.
The estimated non-stop flight time is 10h 11m to 11h 30m, assuming a modern jet cruising at approximately 850 km/h. This gate-to-gate estimate includes time for taxi, takeoff, climb, cruise, descent, and landing. Actual duration varies based on wind conditions — particularly the jet stream — aircraft type, and airport congestion at both ends.
Seoul is 16 hours ahead of Seattle. Travelers crossing 8 time zones westward can expect severe jet lag, with full circadian adjustment typically taking about 6 days.
Since you're traveling westward, your body clock needs to delay — meaning you'll feel alert later into the evening and sluggish in the morning. Evening light exposure at your destination helps push your clock in the right direction.
Route facts: SEA → ICN
| Detail | SEA | ICN |
|---|---|---|
| Airport | Seattle-Tacoma International (SEA) | Incheon International (ICN) |
| City & country | 🇺🇸 Seattle, United States | 🇰🇷 Seoul, South Korea |
| Coordinates | 47.45°N, 122.31°W | 37.46°N, 126.44°E |
| IANA time zone | America/Los_Angeles | Asia/Seoul |
| Current UTC offset | UTC-7 | UTC+9 |
| Local time now | 07:31 | 23:31 |
Flight path, direction and distance
Leaving Seattle, the great-circle track to Seoul starts on an initial bearing of about 310° (NW). The route measures 8,375 km, or 4,522 nautical miles — the unit airlines actually plan with. Because the shortest path on a sphere is a curve rather than a straight line on a flat map, the real track may look like it bends far north or south of the direct line you would draw on a wall map.
At this length the sector counts as ultra-long-haul at around 10h 51m. Aircraft on these rotations carry extra crew, plan an extended dark-cabin period, and fuel load can force payload restrictions on hot days.
This is an international sector, so allow additional time for immigration and customs on arrival — typically 30 to 60 minutes on top of the block time before you are landside.
Departure and arrival times: Seattle to Seoul
Using an estimated block time of 10h 51m and the current offset between the two cities, this table shows what local time you would land in Seoul for common departure times from Seattle. Use it to pick a departure that puts your arrival in daylight, which makes the first day of adjustment much easier.
| Departure (Seattle) | Arrival (Seoul) | Arrival day |
|---|---|---|
| 06:00 | 08:51 | Next day |
| 10:00 | 12:51 | Next day |
| 14:00 | 16:51 | Next day |
| 18:00 | 20:51 | Next day |
| 22:00 | 00:51 | Two days later |
Times are estimates based on great-circle distance and current time zone offsets, not airline schedules. Always confirm with your carrier.
Daylight: Seattle vs Seoul
Daylight length is what actually resets your body clock, and it differs between Seattle and Seoul through the year. In Seoul the day runs from about 9.6 h to 14.8 h across the four dates below, which changes how much morning or evening light you can realistically get after landing.
| Date | Sunrise Seattle | Sunrise Seoul | Sunset Seoul | Day length vs origin |
|---|---|---|---|---|
| March equinox · March 20 | 07:14 | 06:40 | 18:45 | ±0 |
| June solstice · June 21 | 05:12 | 05:13 | 19:58 | −1.2 h |
| September equinox · September 22 | 06:54 | 06:21 | 18:33 | ±0 |
| December solstice · December 21 | 07:54 | 07:45 | 17:19 | +1.1 h |
Your light window in Seoul
Flying west, light in the last hours before sunset holds your clock later, which is the direction you need. In Seoul that window falls around 15:45–18:45. Keep light low around 06:40–09:40. Timing depends on your own circadian phase, so treat these as starting points.
Body clock time on arrival in Seoul
Before any adjustment, your body still runs on Seattle time. When it is 08:00 in Seoul, your body thinks it is 16:00 — which is why local mealtimes and meetings can feel so far off on day one.
| Seoul clock | Your body clock | What your body expects |
|---|---|---|
| 06:00 | 14:00 | Awake and alert |
| 08:00 | 16:00 | Awake and alert |
| 12:00 | 20:00 | Winding down |
| 16:00 | 00:00 | Sleep |
| 20:00 | 04:00 | Deepest sleep, hardest to wake |
| 23:00 | 07:00 | Waking up, low alertness |
Daylight saving on this route in 2026
Seattle (America/Los_Angeles) changes clocks on March 8 (UTC-8 → UTC-7), November 1 (UTC-7 → UTC-8).
Seoul keeps the same offset all year (Asia/Seoul), with no daylight saving changes.
Because the two zones do not switch on the same dates, the gap between Seattle and Seoul is not fixed: it is 17 h in January and 16 h in July. Check the offset for your actual travel date, not a generic value.
Estimated adjustment curve
Westward travel asks your body clock to run later — a phase delay, which most people find easier. Our model uses the CDC-style asymmetric rate: about 1 hour 30 minutes of shift per day westward and 1 hour per day eastward, rounded up to whole days. For 8 time zones that gives about 6 days before local time and body time line up.
Day 1
17% · 6.7 h left
Day 2
33% · 5.3 h left
Day 3
50% · 4 h left
Day 4
67% · 2.7 h left
Day 5
83% · 1.3 h left
Day 6
100% · 0 h left
Return trip: Seoul back to Seattle
| Leg | Direction | Time zones | Modelled recovery |
|---|---|---|---|
| SEA → ICN | westward | 8 | 6 days |
| ICN → SEA | eastward | 8 | 8 days |
The trip home is usually the harder half of this route: about 6 days outbound versus 8 days on the way back, because the return direction asks your clock to shift the way it resists. Plan a lighter first day back in Seattle.