Coriolis Calculator
Coriolis parameter and accel from latitude.
What it does
Earth spin bends moving air and water sideways through the Coriolis effect. Strength is twice spin rate times sine of latitude, times speed. This page runs that product in metric or imperial with direction.
The default is 45 deg with 10 m/s. The parameter is 1.03e-4 /s and accel is 1.03e-3 m/s2 to the right. Imperial converts 22 mph to the same breeze and gives 3.33e-3 ft/s2.
Latitude signs everything. North bends right into highs and lows that spin opposite the south, while the equator gives zero no matter the speed. Poles give the max at the same wind.
Scale decides meaning. Weather and currents feel it across hundreds of kilometers, while sinks and pitchers do not. Use this for sense of size, not for firing tables.
How to use
- Pick metric or imperial first.
- Enter latitude (-90 to 90).
- Enter speed in the active units.
- Read accel first, then f.
- Read direction last.
Formula
- lat
- Latitude in degrees, signed.
- omega
- Earth spin rate per second.
- speed
- Wind or object speed.
Omega is Earth spin 7.2921e-5 rad per s. Latitude signs the turn: positive north bends right, negative south bends left, zero at equator gives none. Speed converts at 1.46667 ft per s per mph behind the scenes.
Worked example
Example: mid latitude breeze
45 deg latitude, 10 m/s (imperial 22 mph).
- Omega: 7.2921e-5 per s (Earth spin).
- f: 2 x 7.2921e-5 x sin45 = 1.03e-4 /s.
- Accel: 1.03e-4 x 10 = 1.03e-3 m/s2.
- Imperial: 22 mph gives 3.33e-3 ft/s2.
- Direction: right in N hemisphere.
- Tool shows 1.03e-3 m/s2 metric.
Reference table
| Latitude | sin | f /s |
|---|---|---|
| 0 deg | 0 | 0 |
| 15 deg | 0.26 | 3.77e-5 |
| 30 deg | 0.5 | 7.29e-5 |
| 45 deg | 0.71 | 1.03e-4 |
| 60 deg | 0.87 | 1.26e-4 |
Limits
- Sense of size only. No trajectory solver.
- Uniform wind assumed. Shear excluded.
- Friction and pressure excluded.
- Sinks and small scales unaffected.
Common mistakes
- Expecting drain spirals from Coriolis.
- Dropping sine of latitude.
- Mixing m/s with mph.
- Reading f as accel without speed.
- Applying at equator.
Try it yourself
Quick checks. Answers sit tucked under each question.
75 deg latitude, 10 m/s?
f 1.41e-4 /s, accel 1.41e-3 m/s2 at 10 m/s.
Equator at 10 m/s?
Zero f and zero accel at any speed.
Questions
Coriolis accel?
Two omega sine latitude times speed. Here 1.03e-3 m/s2.
Coriolis parameter?
2 x 7.2921e-5 x sin(lat). Here 1.03e-4 /s.
Which way?
Right in north, left in south, none at equator.
What is that in imperial?
3.33e-3 ft/s2 for 22 mph at 45 deg.
Bathtub drains?
No. Friction and pressure rule small scales.
Shell paths?
No. Ballistics and weather models add it properly.