In astrophysics, the chirp mass of a compact binary system determines the leading-order orbital evolution of the system as a result of energy loss from emitting gravitational waves. Because the gravitational wave frequency is determined by orbital frequency, the chirp mass also determines the frequency evolution of the gravitational wave signal emitted during a binary's inspiral phase. In gravitational wave data analysis, it is easier to measure the chirp mass than the two component masses alone.

A two-body system with component masses ${\displaystyle m_{1}}$ and ${\displaystyle m_{2}}$ has a chirp mass of

The chirp mass may also be expressed in terms of the total mass of the system ${\displaystyle M=m_{1}+m_{2}}$ and other common mass parameters:

In general relativity, the phase evolution of a binary orbit can be computed using a post-Newtonian expansion, a perturbative expansion in powers of the orbital velocity ${\displaystyle v/c}$. The first order gravitational wave frequency, ${\displaystyle f}$, evolution is described by the differential equation

where ${\displaystyle c}$ and ${\displaystyle G}$ are the speed of light and Newton's gravitational constant, respectively.

If one is able to measure both the frequency ${\displaystyle f}$ and frequency derivative ${\displaystyle {\dot {f}}}$ of a gravitational wave signal, the chirp mass can be determined.

To disentangle the individual component masses in the system one must additionally measure higher order terms in the post-Newtonian expansion.

One limitation of the chirp mass is that it is affected by redshift; what is actually derived from the observed gravitational waveform is the product