  Precise measurements of electroweak processes at the International Linear
Collider (ILC) will provide unique opportunities to explore new physics beyond
the Standard Model. Fermion pair production events are sensitive to new
interactions involving a new heavy gauge boson or an electroweak interacting
massive particle (EWIMP).We studied the mass reach of new particles at the ILC
with $\sqrt{s}=250$ GeV by using $e^+ e^-\to e^+ e^-$and $e^+ e^-\to \mu^+
\mu^-$ events. We show that a mass reach for BSM particles can be determined
with 90% confidence level using a toy Monte Carlo technique.
