In this note we show that an equilibrium measure of a product of two subsets of
C
n
{\mathbb {C}}^{n}
and
C
m
{\mathbb {C}}^{m}
, respectively, is a product of their equilibrium measures. We also obtain a formula for
(
d
d
c
max
{
u
,
v
}
)
p
(dd^{c}\max \{u,v\})^{p}
, where
u
,
v
u,v
are locally bounded plurisubharmonic functions and
2
≤
p
≤
n
2\leq p\leq n
.