Relative Speed Calculator

Compare two constant speeds, choose same or opposite direction, and optionally estimate catch-up or meeting time from an initial separation.

Speed A

Speed B

Speed unit

Directions

Initial separation (optional)Uses the same distance unit implied by km/h→km, mph→mi, or m/s→m.

Interpretation

Catch-up / separation rate

—Relative speed

—m/s

—km/h

—Gap-closing time

—1D rule

Same direction uses the absolute difference of speeds. Opposite directions uses their sum. Gap-closing time assumes the objects are moving along one straight line toward a catch-up or meeting point at constant speeds.

Connected mechanics workflow

v10.88 connects translational motion, forces, momentum, energy, rotation, gravitation, waves and oscillation while preserving the established v2.3/v4.4/v10.38 physics engines.

State the model before trusting the number

Classical formulas are only as good as their assumptions and units. Air resistance, damping, deformation, non-constant forces and measurement uncertainty are not silently invented when the selected model does not include them.

How to use this Relative Speed Calculator

Compare two constant speeds, choose same or opposite direction, and optionally estimate catch-up or meeting time from an initial separation.

What this tool calculates

Calculate 1D relative speed for objects moving in the same or opposite direction.

Practical limits

These are constant-speed, straight-line planning calculations. Real movement can vary with acceleration, stops, route geometry, traffic, terrain, wind, and measurement error.