Cosmic radiation on flights from San Francisco (SFO) to Los Angeles (LAX)

Reverse: Los Angeles → San Francisco

A flight from San Francisco International Airport to Los Angeles International Airport at 35,000 ft, about 56 min in the air, receives about 0.00169 mSv (1.69 µSv) of cosmic radiation: about 2% of a chest X-ray. That is the FAA's CARI-7 model run for this route with the solar conditions of August 2026.

Updated · solar conditions of August 2026

Dose
1.69 µSv0.00169 mSv
Time in the air
56 minestimated
Dose rate
1.8 µSv/haverage, 35,000 ft
Chest X‑rays
0.017at 0.1 mSv each

Key facts: SFO → LAX

Dose, standard flight0.00169 mSv (1.69 µSv)
Time in the air56 min, estimated from distance and prevailing winds
Cruise altitude35,000 ft
Average dose rate1.8 µSv/h
Great-circle distance543 km (337 mi)
Furthest from the equator37.6°N
Solar conditionsAugust 2026

The standard flight is CARI-7, the FAA Civil Aerospace Medical Institute's model, run on the dev machine for this route: 35,000 ft, 56 min in the air (climb 20 min, cruise 19 min, descent 17 min), effective dose per ICRP Publication 103. How it's calculated.

SFOLAX
Great-circle route, shaded from 1.7 µSv/h to 1.9 µSv/h. Shading is modelled from the monthly dose-rate grid; totals are CARI-7.

How the sun changes the dose on SFO → LAX

The sun's 11-year cycle moves this number. With the same 56 min at 35,000 ft, the flight would have received 0.00194 mSv in April 2020, when the sun was quiet and more galactic cosmic rays reached the atmosphere, and 0.00143 mSv in January 2026, near solar maximum: 36% more at the quiet end. In August 2026 it is 0.00169 mSv.

Dose for this flight at 35,000 ft, quarterly
0 µSv1 µSv2 µSv3 µSv2016201820202022202420261.94 µSv1.43 µSv1.69 µSv
0 µSv1 µSv2 µSv3 µSv2016202020241.94 µSv1.43 µSv1.69 µSv
The numbers behind the chart
MonthDoseDose
January 20161.8 µSv0.0018 mSv
April 20161.83 µSv0.00183 mSv
July 20161.82 µSv0.00182 mSv
October 20161.86 µSv0.00186 mSv
January 20171.88 µSv0.00187 mSv
April 20171.9 µSv0.0019 mSv
July 20171.88 µSv0.00188 mSv
October 20171.87 µSv0.00187 mSv
January 20181.89 µSv0.00189 mSv
April 20181.92 µSv0.00192 mSv
July 20181.92 µSv0.00192 mSv
October 20181.94 µSv0.00194 mSv
January 20191.88 µSv0.00188 mSv
April 20191.93 µSv0.00193 mSv
July 20191.92 µSv0.00192 mSv
October 20191.93 µSv0.00193 mSv
January 20201.93 µSv0.00193 mSv
April 20201.94 µSv0.00194 mSv
July 20201.93 µSv0.00193 mSv
October 20201.93 µSv0.00193 mSv
January 20211.89 µSv0.00189 mSv
April 20211.94 µSv0.00194 mSv
July 20211.91 µSv0.00191 mSv
October 20211.91 µSv0.00191 mSv
January 20221.89 µSv0.00189 mSv
April 20221.88 µSv0.00188 mSv
July 20221.78 µSv0.00178 mSv
October 20221.81 µSv0.00181 mSv
January 20231.71 µSv0.00171 mSv
April 20231.72 µSv0.00172 mSv
July 20231.66 µSv0.00166 mSv
October 20231.66 µSv0.00166 mSv
January 20241.6 µSv0.0016 mSv
April 20241.63 µSv0.00163 mSv
July 20241.64 µSv0.00164 mSv
October 20241.49 µSv0.00149 mSv
January 20251.53 µSv0.00153 mSv
April 20251.53 µSv0.00153 mSv
July 20251.52 µSv0.00152 mSv
October 20251.54 µSv0.00154 mSv
January 20261.43 µSv0.00143 mSv
April 20261.56 µSv0.00156 mSv
July 20261.64 µSv0.00164 mSv
August 20261.69 µSv0.00169 mSv

How cruise altitude changes the dose

Flown at 31,000 ft instead, the same flight would receive 0.00125 mSv, 26% less than at 35,000 ft; at 41,000 ft it would receive 0.00242 mSv, 43% more. Same route, same time in the air, same month: only the air overhead changes.

Dose for this flight by cruise altitude, August 2026
  • 31,000 ft1.25 µSv
  • 33,000 ft1.46 µSv
  • 35,000 ft1.69 µSv
  • 37,000 ft1.93 µSv
  • 39,000 ft2.18 µSv
  • 41,000 ft2.42 µSv

Try it: change the altitude and the month

Every combination is its own CARI-7 run for SFO → LAX, with the same 56 min in the air. It is still a standard flight, not yours: the app calculates your exact flight.

Every combination as a table (µSv)
AltitudeJan 2016Jan 2017Jan 2018Jan 2019Jan 2020Jan 2021Jan 2022Jan 2023Jan 2024Jan 2025Jan 2026Aug 2026
31,000 ft1.321.381.391.391.421.391.391.261.181.131.051.25
33,000 ft1.551.621.631.631.671.631.631.481.381.321.231.46
35,000 ft1.81.881.891.881.931.891.891.711.61.531.431.69
37,000 ft2.052.142.162.152.212.162.161.951.821.741.631.93
39,000 ft2.322.422.442.432.492.442.442.22.061.961.832.18
41,000 ft2.582.72.722.712.782.722.722.452.292.182.032.42

The return flight: LAX → SFO

LAX → SFO receives 0.00189 mSv at 35,000 ft, 12% more than SFO → LAX, over about 1 h in the air against 56 min. The two directions take about the same time: the route runs mostly north–south, across the prevailing westerly winds rather than into them.

Dose for each direction, standard flight
  • SFO → LAX1.69 µSv
  • LAX → SFO1.89 µSv

Cosmic radiation on Los Angeles → San Francisco flights

What 1.69 µSv compares with

Compared withIts doseThis flight is
Chest X-Ray0.1 mSvabout 2% of a chest X-ray
Dental X-Ray0.005 mSvabout a third of a dental X-ray
Background Radiation (Daily)0.008 mSvabout a fifth of a day's natural background radiation
Mammogram0.4 mSvabout 1% of a mammogram
Head CT Scan2 mSvabout 1% of a head CT scan
Eating a Banana0.0001 mSvabout 17 bananas

The comparison values are the ones the FlightDose app uses.

Why your flight will differ

  • Altitude. Flown at 31,000 ft instead, the same flight would receive 0.00125 mSv, 26% less than at 35,000 ft; at 41,000 ft it would receive 0.00242 mSv, 43% more. Same route, same time in the air, same month: only the air overhead changes.
  • Time in the air. Every extra 30 minutes on this route adds about 0.91 µSv. Headwinds, holding and routing change it by tens of minutes on a long flight.
  • The month. The sun's 11-year cycle swings this route's dose by about 36% between quiet and active years.
  • The track. Airlines fly tracks that bend with the jet stream, not the exact great circle; a track further from the equator collects more.
  • Solar storms. A rare solar radiation storm can add to the dose for hours; CARI-7's monthly figures don't include one.

FlightDose calculates your exact flight.

Your date, your altitude, your time in the air, with live space weather, and a running total against the limits that matter to you.

Download on the App Store Get it on Google Play

Other routes from SFO

All about San Francisco International Airport

Other routes to LAX

Every published route

Questions people ask

All questions