Flight time & jet lag: London to San Francisco

London to San Francisco: Route overview

This westbound transatlantic route covers 8,616 km from London to San Francisco, crossing the Atlantic with prevailing westerly headwinds that typically extend the 10h 04m to 11h 20m journey by 20–40 minutes compared to the eastbound return. Crossing 8 time zones westbound creates significant circadian disruption. Your body's internal clock will take approximately 6 days to fully realign with San Francisco's local schedule. Both cities sit at similar temperate latitudes, meaning daylight patterns will feel familiar upon arrival — a helpful factor for circadian adjustment.

What makes the London–San Francisco route different

While westbound travel is generally easier than eastbound (your day gets longer rather than shorter), crossing 8 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 San Francisco

Flying west to San Francisco gains you 8 hours, extending your arrival day. At 18:00 local time, your body will think it is 02:00 — 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: London → San Francisco

When you arrive in San Francisco, your circadian rhythm is still running on London time. At 09:00 San Francisco time, your body reads 17:00 — your body's mid-afternoon, meaning you will be alert and functional during the local morning. The main westbound challenge is that by 22:00 local, your body clock reads 06:00 — 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 6 days for full alignment.

Your body clock in San Francisco (day 1)

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

Pre-departure preparation

For this 8-hour westward shift to San Francisco, start 4 days before departure by delaying your bedtime by 120 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 San Francisco's daytime. This gradual shift can significantly ease your transition upon arrival.

Your first 72 hours in San Francisco

Day 1 in San Francisco: Your body is ~8 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: ~7 hours off. Continue late afternoon (15:00–18:00) light exposure. Sleep quality should improve. Day 3: ~5 hours off. Noticeable improvement. Maintain light and meal timing discipline.

Recovery timeline

Full circadian adjustment for the London → San Francisco route typically takes 6 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 6, most travelers report feeling fully synchronized with San Francisco's schedule.

Route Planner

Adjust departure date for DST-accurate results.

Jet lag adjustment plan: London → San Francisco

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

Business hours: London vs San Francisco

Seasonal and climate factors

Transatlantic flight times between London and San Francisco vary seasonally: winter jet streams can reduce eastbound flights by 30–45 minutes while extending westbound flights by a similar amount. Summer typically sees more moderate wind patterns. San Francisco at 38°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 London–San Francisco flight time is estimated

The 10h 04m to 11h 20m estimate for London to San Francisco is derived from the 8,616-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 LHR and SFO. 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

Westbound flights from London to San Francisco fly against the North Atlantic jet stream, adding time compared to the eastbound leg. Airlines often route these flights on more southerly tracks to minimize headwind exposure, which increases the path distance but can still reduce total time.

Practical travel context

As a transatlantic connection between London and San Francisco, this route is primarily served by full-service carriers with seasonal charter supplements. Direct flights typically use wide-body aircraft suited to the 8,616-km distance. For stays shorter than 8 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: London to San Francisco

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