  The absolute branching ratio of the $K^+ \rightarrow \pi^+\pi^-\pi^+(\gamma)$
decay, inclusive of final-state radiation, has been measured using $\sim$17
million tagged $K^+$ mesons collected with the KLOE detector at DA$\Phi$NE, the
Frascati $\phi$-factory. The result is:
  \[ BR(K^+ \rightarrow \pi^+\pi^-\pi^+(\gamma)) = 0.05565 \pm 0.00031_{stat}
\pm 0.00025_{syst} \] a factor $\simeq$ 5 more precise with respect to the
previous result. This work completes the program of precision measurements of
the dominant kaon branching ratios at KLOE.
