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Both calculators run independently — change the inputs on either side to compare results.

Relativistic Velocity Addition Calculator

Computes the combined velocity of two objects moving at relativistic speeds, preventing any result from exceeding the speed of light. Use it when simple addition of velocities would violate special relativity.

Velocity 1 (m/s)

Velocity 2 (m/s)

Direction

Velocity Unit

Fill in the required fields to see your result.

Relativity

Relativistic Doppler Shift Calculator

Calculates the observed frequency of light or sound when source and observer move at relativistic speeds. Use it when relative velocity is a significant fraction of the speed of light.

Rest Frequency (Hz)

Relative Velocity (m/s)

Direction

Fill in the required fields to see your result.

Key differences

	Relativistic Velocity Addition Calculator	Relativistic Doppler Shift Calculator
Category	Relativity	Relativity
Inputs required	4	3
Result	Relativistic Sum (m/s)	Observed Frequency (Hz)
What it does	Computes the combined velocity of two objects moving at relativistic speeds, preventing any result from exceeding the speed of light. Use it when simple addition of velocities would violate special relativity.	Calculates the observed frequency of light or sound when source and observer move at relativistic speeds. Use it when relative velocity is a significant fraction of the speed of light.