Flight time & jet lag: Seoul to Seattle

Seoul to Seattle: Route overview

This eastbound Pacific crossing from Seoul to Seattle covers 8,375 km in approximately 9h 48m to 11h 03m, benefiting from the jet stream but crossing 17 time zones — a significant circadian challenge. At 17 time zones crossed westbound, this is among the most demanding routes for jet lag. Full adjustment typically requires 7 days of deliberate sleep and light management. Both cities sit at similar temperate latitudes, meaning daylight patterns will feel familiar upon arrival — a helpful factor for circadian adjustment.

What makes the Seoul–Seattle route different

While westbound travel is generally easier than eastbound (your day gets longer rather than shorter), crossing 17 time zones still creates substantial disruption. The advantage is that most people find it easier to stay awake past their usual bedtime than to fall asleep earlier.

Arrival strategy for Seattle

Flying west to Seattle gains you 17 hours, extending your arrival day. At 18:00 local time, your body will think it is 11:00 — meaning you will feel ready for sleep well before the local bedtime. Counter this by getting bright light in the late afternoon and early evening. Eat dinner at the local time, stay physically active, and push your bedtime to at least 21:00 local. Avoid morning light before 08:00 on the first few days, as this would advance your clock in the wrong direction.

Circadian rhythm analysis: Seoul → Seattle

When you arrive in Seattle, your circadian rhythm is still running on Seoul time. At 09:00 Seattle time, your body reads 02:00 — a reasonable waking hour internally, so morning performance should be manageable. The main westbound challenge is that by 22:00 local, your body clock reads 15:00 — past your natural bedtime. You will likely feel premature sleepiness in the late afternoon or early evening. Your circadian system adjusts at roughly 1 to 1.5 hours per day, so expect 7 days for full alignment.

Your body clock in Seattle (day 1)

How your body clock maps to local time upon arrival, before any adjustment.

Pre-departure preparation

For this 17-hour westward shift to Seattle, start 4 days before departure by delaying your bedtime by 255 minutes each night. Seek bright light in the evening hours to help push your clock later. On the flight, try to stay awake if arriving during Seattle's daytime. This gradual shift can significantly ease your transition upon arrival.

Your first 72 hours in Seattle

Day 1 in Seattle: Your body is ~17 hours off local time. Stay active and seek afternoon sunlight. Push bedtime to at least 21:00 local. Eat at local mealtimes even if not hungry. Caffeine is fine before 16:00, not after. Day 2: ~16 hours off. Continue late afternoon (15:00–18:00) light exposure. Sleep quality should improve. Day 3: ~14 hours off. Noticeable improvement. Maintain light and meal timing discipline.

Recovery timeline

Full circadian adjustment for the Seoul → Seattle route typically takes 7 days, based on the body's natural adaptation rate of ~1 to 1.5 hours per day for westbound travel. During this period, expect gradually improving sleep quality, with the most noticeable symptoms (fatigue, difficulty concentrating, appetite changes) during the first 3 days. By day 7, most travelers report feeling fully synchronized with Seattle's schedule.

Route Planner

Adjust departure date for DST-accurate results.

Jet lag adjustment plan: Seoul → Seattle

Significant jet lag. Allow 4–7 days for full adjustment. Plan sleep and light exposure carefully.

Business hours: Seoul vs Seattle

Seasonal and climate factors

Transpacific winds between Seoul and Seattle shift seasonally, with the winter jet stream creating the largest outbound/return time differential. Spring and autumn typically offer the most predictable flight times. Seattle at 47°N experiences moderate seasonal daylight variation. Summer offers longer evenings useful for westward adjustment, while winter's earlier sunsets support eastward adjustment schedules.

How the Seoul–Seattle flight time is estimated

The 9h 48m to 11h 03m estimate for Seoul to Seattle is derived from the 8,375-km great-circle distance. Long-haul flights spend most of their duration at optimal cruise altitude (typically 35,000–40,000 feet), achieving effective speeds of 820–900 km/h. An additional 30–50 minutes accounts for taxi, takeoff, climb, descent, approach, and taxi at both ICN and SEA. This oceanic route means actual flight paths follow organized track systems that may deviate from the great-circle distance, potentially adding 5–10% to the theoretical minimum path. Prevailing winds along this corridor can shift the actual time by 20–60 minutes in either direction.

Wind patterns and flight duration

Pacific routes between Seoul and Seattle are significantly affected by the Pacific jet stream. Westbound flights avoid the jet stream by routing further south or north, adding distance but mitigating headwinds. The differential between outbound and return times on this route can exceed 1 hour.

Practical travel context

Transpacific routes between Seoul and Seattle are among the longest commercial routes, typically operated by wide-body aircraft with adequate range for the 8,375-km journey. For stays shorter than 9 days, some travelers opt not to fully adjust to local time. Instead, they maintain a compromise schedule between origin and destination time, which can be effective for brief business trips.

Frequently asked questions: Seoul to Seattle

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