Coriolis Effect Calculator

About the Coriolis Effect Calculator

The Coriolis effect is an apparent deflection of moving objects when viewed from a rotating reference frame — most importantly, the rotating Earth. In the Northern Hemisphere, objects are deflected to the right of their direction of motion; in the Southern Hemisphere, to the left. This effect is negligible for small-scale motion but dominates large-scale atmospheric and oceanic circulation.

This calculator computes the Coriolis parameter (f = 2Ω sin φ), Coriolis acceleration, lateral deflection distance, and the Rossby number (which determines whether Coriolis effects matter for a given scenario). Presets include artillery shells, sniper rounds, ICBMs, hurricanes, trade winds, and soccer balls.

The latitude comparison table shows how the effect strengthens from the equator (zero) to the poles (maximum), while the scale comparison table clarifies which real-world phenomena are significantly affected by the Coriolis force and which are not. It also helps show why the same rotation matters for weather systems but is negligible for small handheld motions.

When This Page Helps

The Coriolis effect calculator is essential for understanding atmospheric science (weather system rotation), oceanography (ocean gyre circulation), military ballistics (artillery and long-range fire correction), and aerospace engineering (ICBM trajectory planning).

The Rossby number analysis immediately tells you whether the Coriolis effect matters for your specific scenario, preventing both over-correction on small scales and under-correction on large ones. It also gives a fast way to compare real projects against the scale where rotation actually changes the motion.

How to Use the Inputs

1. Select analysis mode: projectile deflection or Coriolis acceleration/force.
2. Enter the object velocity in m/s.
3. Enter the latitude (negative for Southern Hemisphere).
4. Enter the flight or travel time in seconds.
5. For acceleration mode, enter the object mass to get Coriolis force.
6. Review deflection, Coriolis parameter, Rossby number, and direction from outputs.

Example Calculation

Tips & Best Practices

• At the equator (0° latitude), the Coriolis parameter is zero — no deflection.
• The Coriolis effect is maximum at the poles (90° latitude).
• Deflection is to the RIGHT in the Northern Hemisphere, LEFT in the Southern.
• If the Rossby number is much greater than 1, forget about Coriolis.
• Coriolis deflection scales with t² — it compounds rapidly over time.
• The Coriolis force never does work (always perpendicular to velocity) — it only deflects.

The Coriolis Effect in Meteorology

Global wind patterns are fundamentally shaped by the Coriolis effect. Trade winds blow from east to west near the equator because air moving toward the equator is deflected westward. Mid-latitude westerlies blow from west to east because poleward-moving air is deflected eastward. The Coriolis effect also creates the geostrophic wind balance, where pressure gradient force and Coriolis force balance to produce winds parallel to isobars rather than across them.

Foucault Pendulum and Earth's Rotation

The Foucault pendulum demonstrates the Coriolis effect directly: a freely swinging pendulum appears to rotate its plane of oscillation at a rate of 360° × sin(φ) per day. At the North Pole, the plane completes a full rotation in 24 hours. At 45° latitude, it takes about 33.9 hours.

Coriolis in Engineering Design

Engineers account for the Coriolis effect in Coriolis flow meters, which measure mass flow rate by detecting the Coriolis force on fluid flowing through vibrating tubes. The same principle affects river erosion (right bank erosion in the Northern Hemisphere), railroad track wear, and long-range projectile guidance systems.

Frequently Asked Questions

• Does the Coriolis effect really affect bathtub drains?

  No. The Coriolis force on bathtub-scale flows is about 10 million times weaker than other forces (basin shape, residual currents, drain geometry). The direction of a bathtub vortex is essentially random and has nothing to do with hemisphere.

• Why is there no Coriolis effect at the equator?

  The Coriolis parameter f = 2Ω sin(φ) equals zero at the equator (φ = 0°) because horizontal motion at the equator is parallel to the rotation axis. The Coriolis force only acts perpendicular to the rotation axis, which has no horizontal component at the equator.

• How does the Coriolis effect create hurricanes?

  Low-pressure systems draw air inward. The Coriolis effect deflects this inward-flowing air to the right (Northern Hemisphere), creating counterclockwise rotation. This is why hurricanes spin counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere. The effect is too weak near the equator (within ~5°) to create tropical cyclones.

• What is the Rossby number?

  The Rossby number Ro = v/(fL) compares inertial forces to Coriolis forces. When Ro >> 1, the Coriolis effect is negligible (small-scale, fast phenomena). When Ro << 1, the Coriolis effect dominates (large-scale, slow phenomena like weather systems and ocean currents).

• Do snipers need to account for the Coriolis effect?

  For long-range shots (1+ km), yes. A typical sniper round deflects about 7-15 cm per kilometer due to Coriolis at mid-latitudes. At extreme ranges (2+ km), the deflection exceeds typical target width and must be corrected.

• Does the Coriolis effect apply on other planets?

  Yes, any rotating body exhibits the Coriolis effect. Jupiter's intense banding and Great Red Spot are shaped by strong Coriolis effects (Jupiter rotates in 10 hours). Mars has weaker effects (24.6 hour rotation) but they still influence dust storms and atmospheric circulation.