Calculate Coriolis deflection, acceleration, and force for moving objects on a rotating Earth. Analyze projectiles, weather systems, and ocean currents.
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. Check the example with realistic values before reporting.
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.
Coriolis parameter: f = 2Ω sin(φ), where Ω = 7.292 × 10⁻⁵ rad/s. Coriolis acceleration: a = 2Ωv sin(φ). Lateral deflection: d ≈ ½ × a × t². Rossby number: Ro = v / (f × L). Inertial period: T = 2π / |f|.
Result: 100.5 m deflection to the right
An artillery shell traveling at 800 m/s for 30 seconds at 45°N latitude is deflected approximately 100 meters to the right. This is military-significant and must be corrected in fire control calculations for long-range gunnery.
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.
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.
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.
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.
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.
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.
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).
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.
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.