Cosmic radiation on flights from Singapore (SIN) to San Francisco (SFO)
Reverse: San Francisco → Singapore
A flight from Singapore Changi Airport to San Francisco International Airport at 35,000 ft, about 15 h 24 min in the air, receives about 0.0391 mSv (39.1 µSv) of cosmic radiation: about 39% 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
- 39.1 µSv0.0391 mSv
- Time in the air
- 15 h 24 minestimated
- Dose rate
- 2.5 µSv/haverage, 35,000 ft
- Chest X‑rays
- 0.39at 0.1 mSv each
Key facts: SIN → SFO
| Dose, standard flight | 0.0391 mSv (39.1 µSv) |
|---|---|
| Time in the air | 15 h 24 min, estimated from distance and prevailing winds |
| Cruise altitude | 35,000 ft |
| Average dose rate | 2.5 µSv/h |
| Great-circle distance | 13,582 km (8,439 mi) |
| Furthest from the equator | 47.4°N |
| Solar conditions | August 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, 15 h 24 min in the air (climb 25 min, cruise 882 min, descent 17 min), effective dose per ICRP Publication 103. How it's calculated.
How the sun changes the dose on SIN → SFO
The sun's 11-year cycle moves this number. With the same 15 h 24 min at 35,000 ft, the flight would have received 0.044 mSv in April 2020, when the sun was quiet and more galactic cosmic rays reached the atmosphere, and 0.0339 mSv in January 2026, near solar maximum: 30% more at the quiet end. In August 2026 it is 0.0391 mSv.
The numbers behind the chart
| Month | Dose | Dose |
|---|---|---|
| January 2016 | 41.2 µSv | 0.0412 mSv |
| April 2016 | 41.8 µSv | 0.0418 mSv |
| July 2016 | 41.7 µSv | 0.0417 mSv |
| October 2016 | 42.5 µSv | 0.0425 mSv |
| January 2017 | 42.7 µSv | 0.0427 mSv |
| April 2017 | 43.3 µSv | 0.0433 mSv |
| July 2017 | 42.9 µSv | 0.0429 mSv |
| October 2017 | 42.7 µSv | 0.0427 mSv |
| January 2018 | 43 µSv | 0.043 mSv |
| April 2018 | 43.6 µSv | 0.0436 mSv |
| July 2018 | 43.5 µSv | 0.0435 mSv |
| October 2018 | 44 µSv | 0.044 mSv |
| January 2019 | 42.9 µSv | 0.0429 mSv |
| April 2019 | 43.9 µSv | 0.0439 mSv |
| July 2019 | 43.6 µSv | 0.0436 mSv |
| October 2019 | 43.9 µSv | 0.0439 mSv |
| January 2020 | 43.8 µSv | 0.0438 mSv |
| April 2020 | 44 µSv | 0.044 mSv |
| July 2020 | 43.8 µSv | 0.0438 mSv |
| October 2020 | 43.8 µSv | 0.0438 mSv |
| January 2021 | 43.1 µSv | 0.0431 mSv |
| April 2021 | 43.9 µSv | 0.0439 mSv |
| July 2021 | 43.4 µSv | 0.0434 mSv |
| October 2021 | 43.5 µSv | 0.0435 mSv |
| January 2022 | 43 µSv | 0.043 mSv |
| April 2022 | 42.8 µSv | 0.0428 mSv |
| July 2022 | 40.9 µSv | 0.0409 mSv |
| October 2022 | 41.5 µSv | 0.0415 mSv |
| January 2023 | 39.5 µSv | 0.0395 mSv |
| April 2023 | 39.8 µSv | 0.0398 mSv |
| July 2023 | 38.5 µSv | 0.0385 mSv |
| October 2023 | 38.6 µSv | 0.0386 mSv |
| January 2024 | 37.3 µSv | 0.0373 mSv |
| April 2024 | 37.9 µSv | 0.0379 mSv |
| July 2024 | 38.1 µSv | 0.0381 mSv |
| October 2024 | 35.2 µSv | 0.0352 mSv |
| January 2025 | 35.9 µSv | 0.0359 mSv |
| April 2025 | 36 µSv | 0.036 mSv |
| July 2025 | 35.7 µSv | 0.0357 mSv |
| October 2025 | 36.3 µSv | 0.0363 mSv |
| January 2026 | 33.9 µSv | 0.0339 mSv |
| April 2026 | 36.6 µSv | 0.0366 mSv |
| July 2026 | 38.1 µSv | 0.0381 mSv |
| August 2026 | 39.1 µSv | 0.0391 mSv |
How cruise altitude changes the dose
Flown at 31,000 ft instead, the same flight would receive 0.029 mSv, 26% less than at 35,000 ft; at 41,000 ft it would receive 0.0544 mSv, 39% more. Same route, same time in the air, same month: only the air overhead changes.
Try it: change the altitude and the month
Every combination is its own CARI-7 run for SIN → SFO, with the same 15 h 24 min in the air. It is still a standard flight, not yours: the app calculates your exact flight.
Every combination as a table (µSv)
| Altitude | Jan 2016 | Jan 2017 | Jan 2018 | Jan 2019 | Jan 2020 | Jan 2021 | Jan 2022 | Jan 2023 | Jan 2024 | Jan 2025 | Jan 2026 | Aug 2026 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 31,000 ft | 30.6 | 31.7 | 31.9 | 31.8 | 32.4 | 31.9 | 31.9 | 29.4 | 27.7 | 26.7 | 25.3 | 29 |
| 33,000 ft | 35.8 | 37.1 | 37.4 | 37.2 | 38 | 37.4 | 37.3 | 34.3 | 32.4 | 31.2 | 29.5 | 34 |
| 35,000 ft | 41.2 | 42.7 | 43 | 42.9 | 43.8 | 43.1 | 43 | 39.5 | 37.3 | 35.9 | 33.9 | 39.1 |
| 37,000 ft | 46.8 | 48.5 | 48.9 | 48.7 | 49.7 | 48.9 | 48.8 | 44.8 | 42.3 | 40.7 | 38.4 | 44.3 |
| 39,000 ft | 52.3 | 54.3 | 54.7 | 54.4 | 55.6 | 54.7 | 54.6 | 50 | 47.2 | 45.3 | 42.8 | 49.5 |
| 41,000 ft | 57.5 | 59.7 | 60.2 | 59.9 | 61.2 | 60.2 | 60.1 | 55 | 51.8 | 49.7 | 46.8 | 54.4 |
The return flight: SFO → SIN
SFO → SIN receives 0.0424 mSv at 35,000 ft, 8% more than SIN → SFO, over about 16 h 42 min in the air against 15 h 24 min. The return takes 1 h 18 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.
What 39.1 µSv compares with
| Compared with | Its dose | This flight is |
|---|---|---|
| Chest X-Ray | 0.1 mSv | about 39% of a chest X-ray |
| Dental X-Ray | 0.005 mSv | about 7.8 dental X-rays |
| Background Radiation (Daily) | 0.008 mSv | about 4.9 days of natural background radiation |
| Mammogram | 0.4 mSv | about a tenth of a mammogram |
| Head CT Scan | 2 mSv | about 2% of a head CT scan |
| Eating a Banana | 0.0001 mSv | about 391 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 0.029 mSv, 26% less than at 35,000 ft; at 41,000 ft it would receive 0.0544 mSv, 39% 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 1.3 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 30% 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.