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

Reverse: San Francisco → Los Angeles

A flight from Los Angeles International Airport to San Francisco International Airport at 35,000 ft, about 1 h in the air, receives about 0.00189 mSv (1.89 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
1.89 µSv0.00189 mSv
Time in the air
1 hestimated
Dose rate
1.9 µSv/haverage, 35,000 ft
Chest X‑rays
0.019at 0.1 mSv each

Key facts: LAX → SFO

Dose, standard flight0.00189 mSv (1.89 µSv)
Time in the air1 h, estimated from distance and prevailing winds
Cruise altitude35,000 ft
Average dose rate1.9 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, 1 h in the air (climb 21 min, cruise 22 min, descent 17 min), effective dose per ICRP Publication 103. How it's calculated.

LAXSFO
Great-circle route, shaded from 1.8 µSv/h to 2.0 µSv/h. Shading is modelled from the monthly dose-rate grid; totals are CARI-7.

How the sun changes the dose on LAX → SFO

The sun's 11-year cycle moves this number. With the same 1 h at 35,000 ft, the flight would have received 0.00217 mSv in April 2020, when the sun was quiet and more galactic cosmic rays reached the atmosphere, and 0.00159 mSv in January 2026, near solar maximum: 36% more at the quiet end. In August 2026 it is 0.00189 mSv.

Dose for this flight at 35,000 ft, quarterly
0 µSv1 µSv2 µSv3 µSv2016201820202022202420262.17 µSv1.59 µSv1.89 µSv
0 µSv1 µSv2 µSv3 µSv2016202020242.17 µSv1.59 µSv1.89 µSv
The numbers behind the chart
MonthDoseDose
January 20162.01 µSv0.00201 mSv
April 20162.04 µSv0.00204 mSv
July 20162.04 µSv0.00204 mSv
October 20162.08 µSv0.00208 mSv
January 20172.1 µSv0.0021 mSv
April 20172.13 µSv0.00213 mSv
July 20172.1 µSv0.0021 mSv
October 20172.09 µSv0.00209 mSv
January 20182.11 µSv0.00211 mSv
April 20182.15 µSv0.00215 mSv
July 20182.14 µSv0.00214 mSv
October 20182.17 µSv0.00216 mSv
January 20192.1 µSv0.0021 mSv
April 20192.16 µSv0.00216 mSv
July 20192.14 µSv0.00214 mSv
October 20192.16 µSv0.00216 mSv
January 20202.15 µSv0.00215 mSv
April 20202.17 µSv0.00217 mSv
July 20202.16 µSv0.00216 mSv
October 20202.16 µSv0.00216 mSv
January 20212.11 µSv0.00211 mSv
April 20212.16 µSv0.00216 mSv
July 20212.13 µSv0.00213 mSv
October 20212.14 µSv0.00214 mSv
January 20222.11 µSv0.00211 mSv
April 20222.1 µSv0.0021 mSv
July 20221.99 µSv0.00199 mSv
October 20222.03 µSv0.00203 mSv
January 20231.91 µSv0.00191 mSv
April 20231.93 µSv0.00193 mSv
July 20231.85 µSv0.00185 mSv
October 20231.86 µSv0.00186 mSv
January 20241.78 µSv0.00178 mSv
April 20241.82 µSv0.00182 mSv
July 20241.83 µSv0.00183 mSv
October 20241.66 µSv0.00166 mSv
January 20251.7 µSv0.0017 mSv
April 20251.7 µSv0.0017 mSv
July 20251.69 µSv0.00169 mSv
October 20251.72 µSv0.00172 mSv
January 20261.59 µSv0.00159 mSv
April 20261.74 µSv0.00174 mSv
July 20261.83 µSv0.00183 mSv
August 20261.89 µSv0.00189 mSv

How cruise altitude changes the dose

Flown at 31,000 ft instead, the same flight would receive 0.00139 mSv, 26% less than at 35,000 ft; at 41,000 ft it would receive 0.0027 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 ft1.39 µSv
  • 33,000 ft1.63 µSv
  • 35,000 ft1.89 µSv
  • 37,000 ft2.15 µSv
  • 39,000 ft2.43 µSv
  • 41,000 ft2.7 µSv

Try it: change the altitude and the month

Every combination is its own CARI-7 run for LAX → SFO, with the same 1 h 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 ft1.481.541.551.551.581.561.551.411.311.261.171.39
33,000 ft1.731.811.821.821.861.821.821.651.541.471.381.63
35,000 ft2.012.12.112.12.152.112.111.911.781.71.591.89
37,000 ft2.292.42.422.42.472.422.412.182.031.941.812.15
39,000 ft2.592.72.732.712.782.732.722.462.292.192.042.43
41,000 ft2.883.013.043.023.13.043.042.742.552.432.262.7

The return flight: SFO → LAX

SFO → LAX receives 0.00169 mSv at 35,000 ft, 10% less than LAX → SFO, over about 56 min in the air against 1 h. 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
  • LAX → SFO1.89 µSv
  • SFO → LAX1.69 µSv

Cosmic radiation on San Francisco → Los Angeles flights

What 1.89 µSv compares with

Compared withIts doseThis flight is
Chest X-Ray0.1 mSvabout 2% of a chest X-ray
Dental X-Ray0.005 mSvabout 38% of a dental X-ray
Background Radiation (Daily)0.008 mSvabout a quarter 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 19 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 0.00139 mSv, 26% less than at 35,000 ft; at 41,000 ft it would receive 0.0027 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 0.94 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 LAX

All about Los Angeles International Airport

Other routes to SFO

Every published route

Questions people ask

All questions