  We prove a set of tight entanglement inequalities for arbitrary $N$-qubit
pure states. By focusing on all bi-partite marginal entanglements between each
single qubit and its remaining partners, we show that the inequalities provide
an upper bound for each marginal entanglement, while the known monogamy
relation establishes the lower bound. The restrictions and sharing properties
associated with the inequalities are further analyzed with a geometric polytope
approach, and examples of three-qubit GHZ-class and W-class entangled states
are presented to illustrate the results.
