Cosmic radiation on flights from San Francisco (SFO) to New York (JFK)

Reverse: New York → San Francisco

A flight from San Francisco International Airport to John F. Kennedy International Airport at 35,000 ft, about 4 h 45 min in the air, receives about 0.0185 mSv (18.5 µSv) of cosmic radiation: about a fifth 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
18.5 µSv0.0185 mSv
Time in the air
4 h 45 minestimated
Dose rate
3.9 µSv/haverage, 35,000 ft
Chest X‑rays
0.18at 0.1 mSv each

Key facts: SFO → JFK

Dose, standard flight0.0185 mSv (18.5 µSv)
Time in the air4 h 45 min, estimated from distance and prevailing winds
Cruise altitude35,000 ft
Average dose rate3.9 µSv/h
Great-circle distance4,152 km (2,580 mi)
Furthest from the equator42.0°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, 4 h 45 min in the air (climb 25 min, cruise 243 min, descent 17 min), effective dose per ICRP Publication 103. How it's calculated.

SFOJFK
Great-circle route, shaded from 3.4 µSv/h to 4.2 µSv/h. Shading is modelled from the monthly dose-rate grid; totals are CARI-7.

How the sun changes the dose on SFO → JFK

The sun's 11-year cycle moves this number. With the same 4 h 45 min at 35,000 ft, the flight would have received 0.023 mSv in April 2020, when the sun was quiet and more galactic cosmic rays reached the atmosphere, and 0.0145 mSv in January 2026, near solar maximum: 59% more at the quiet end. In August 2026 it is 0.0185 mSv.

Dose for this flight at 35,000 ft, quarterly
0 µSv10 µSv20 µSv30 µSv20162018202020222024202623 µSv14.5 µSv18.5 µSv
0 µSv10 µSv20 µSv30 µSv20162020202423 µSv14.5 µSv18.5 µSv
The numbers behind the chart
MonthDoseDose
January 201620.3 µSv0.0203 mSv
April 201620.9 µSv0.0209 mSv
July 201620.8 µSv0.0208 mSv
October 201621.5 µSv0.0215 mSv
January 201721.8 µSv0.0218 mSv
April 201722.3 µSv0.0223 mSv
July 201721.9 µSv0.0219 mSv
October 201721.7 µSv0.0217 mSv
January 201822.1 µSv0.0221 mSv
April 201822.6 µSv0.0226 mSv
July 201822.5 µSv0.0225 mSv
October 201823 µSv0.023 mSv
January 201921.9 µSv0.0219 mSv
April 201922.9 µSv0.0229 mSv
July 201922.6 µSv0.0226 mSv
October 201922.9 µSv0.0229 mSv
January 202022.8 µSv0.0228 mSv
April 202023 µSv0.023 mSv
July 202022.8 µSv0.0228 mSv
October 202022.8 µSv0.0228 mSv
January 202122.1 µSv0.0221 mSv
April 202122.9 µSv0.0229 mSv
July 202122.4 µSv0.0224 mSv
October 202122.5 µSv0.0225 mSv
January 202222 µSv0.022 mSv
April 202221.8 µSv0.0218 mSv
July 202220 µSv0.02 mSv
October 202220.7 µSv0.0207 mSv
January 202318.9 µSv0.0189 mSv
April 202319.1 µSv0.0191 mSv
July 202318 µSv0.018 mSv
October 202318.1 µSv0.0181 mSv
January 202417 µSv0.017 mSv
April 202417.5 µSv0.0175 mSv
July 202417.7 µSv0.0177 mSv
October 202415.4 µSv0.0154 mSv
January 202515.9 µSv0.0159 mSv
April 202516 µSv0.016 mSv
July 202515.8 µSv0.0158 mSv
October 202516.2 µSv0.0162 mSv
January 202614.5 µSv0.0145 mSv
April 202616.5 µSv0.0165 mSv
July 202617.7 µSv0.0177 mSv
August 202618.5 µSv0.0185 mSv

How cruise altitude changes the dose

Flown at 31,000 ft instead, the same flight would receive 0.0134 mSv, 27% less than at 35,000 ft; at 41,000 ft it would receive 0.0268 mSv, 45% 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 ft13.4 µSv
  • 33,000 ft15.9 µSv
  • 35,000 ft18.5 µSv
  • 37,000 ft21.2 µSv
  • 39,000 ft24 µSv
  • 41,000 ft26.8 µSv

Try it: change the altitude and the month

Every combination is its own CARI-7 run for SFO → JFK, with the same 4 h 45 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 ft14.715.715.915.816.415.915.913.712.411.610.613.4
33,000 ft17.418.618.918.819.518.918.816.214.613.712.515.9
35,000 ft20.321.822.121.922.822.12218.91715.914.518.5
37,000 ft23.42525.425.226.225.425.321.619.518.316.621.2
39,000 ft26.528.428.928.629.828.928.824.522.120.618.724
41,000 ft29.731.932.332.133.532.432.327.424.622.920.726.8

The return flight: JFK → SFO

JFK → SFO receives 0.0219 mSv at 35,000 ft, 18% more than SFO → JFK, over about 5 h 32 min in the air against 4 h 45 min. The return takes 47 min longer: its track runs against the prevailing westerly winds at cruise altitude. Cosmic radiation builds up with every minute aloft, so the longer direction collects more of it along the same path.

Dose for each direction, standard flight
  • SFO → JFK18.5 µSv
  • JFK → SFO21.9 µSv

Cosmic radiation on New York → San Francisco flights

What 18.5 µSv compares with

Compared withIts doseThis flight is
Chest X-Ray0.1 mSvabout a fifth of a chest X-ray
Dental X-Ray0.005 mSvabout 3.7 dental X-rays
Background Radiation (Daily)0.008 mSvabout 2.3 days of natural background radiation
Mammogram0.4 mSvabout 5% of a mammogram
Head CT Scan2 mSvabout 1% of a head CT scan
Eating a Banana0.0001 mSvabout 185 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 0.0134 mSv, 27% less than at 35,000 ft; at 41,000 ft it would receive 0.0268 mSv, 45% 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 1.9 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 59% 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.

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